Interview by Richard Marshall.

Michail Peramatzis' specialities are ancient philosophy, especially Aristotle's metaphysics, logic and epistemology and Plato's metaphysics and epistemology. Here he carefully and thoroughly discusses philosophical intuitions about Aristotle's metaphysics, dependence and independence relations in Aristotle, how he links Aristotelian metaphysics to contemporary concerns, its relationship with Quine, ontological priority, Kit Fine's influence, essences and their essences, Aristotle’s hylomorphism and whether his causal-explanatory model of essence and definition is applicable to substance-kinds. You'll get the hang of this if you read on. If Aristotle never left here are some passionately and incisively expressed reasons why we still should think about him. Carve out some time for this one ...

3:AM:What made you become a philosopher?

Michail Peramatzis:Early on at Junior High School (what is called ‘Gymnasium’ in Greek secondary education), when I was about 12, my Classics and Literature teacher told me that my writings read a lot like a University student’s writings in quality and style. While I enjoyed studying language, grammar, and linguistics anyhow, I took this as a compliment and started thinking more seriously that I should aim at reading a Humanities degree, probably Classics. Many other teachers tried to persuade me to read medicine (a more sensible choice) but failed. A few years later in Senior High School (‘Lyceum’) I was determined to sit exams to read classics.

At the same time, through my interests in history, music, film, and art generally, I started thinking about philosophical questions –mainly in ethics and politics. I saw that Plato’s and Aristotle’s works were among the most important starting-points for study in these areas. This strengthened my resolve to study Classics. So, when I entered my university options, instead of choosing a straight Classics degree, I chose ‘Philosophy, Pedagogics, and Psychology’. I did this partly out of lack of information and partly out of the explicit mention of philosophy in the title of the degree. This undergraduate degree was in effect a classics programme with a lot of philosophy in it.

During my studies for that degree two things happened that, I think, made me become a philosopher. First, I read a few of Nietzsche’s works (Thus Spoke Zarathustra, Twilight of the Gods, The Birth of Tragedy). I wrote a university essay on the aphorisms introducing the Twilight of the Godstrying to make logical sense and come up with a coherent interpretation of Nietzsche’s ideas. I concluded that my method was not perfectly suited to this subject-matter. Shortly after that (this is the second point) I took a course that included sections of Karl Popper’s Conjectures and Refutations. I was so excited with the clarity of presentation, the rigour of reasoning (compared with philosophers I had read up to that point), and the interesting questions raised and addressed: Popper’s view of the growth of scientific knowledge but also his criticism of what he thought was unscientific or pseudoscientific disciplines. I remember that his argument in ‘What is Dialectic?’, especially his use of (very basic) logical notation, made me decide that I wanted to study further logic and the philosophy of science. This led me to my Master’s degree in the Philosophy and History of Science. One of the courses for this degree was on Aristotle’s Posterior Analytics. Studying this work satisfied not only my interest in the philosophy of science and logic but also my love of classics. It definitely made me become the sort of philosopher I now am.

3:AM:You’re an expert in Aristotelian metaphysics. You’ve written about what you call ‘priority relations between fundamental and derivative parts of reality.’ Ok, so can you unpack that so we can see what the issues are and what’s at stake in this?

MP:One aspect of what I tried to do in 'Priority in Aristotle’s Metaphysics' was to have a philosophical understanding of Aristotelian intuitions –which, I think, are shared with common sense– about what sorts of entity or object are basic and what are somehow parasitic upon them. Aristotle thought that ‘middle-sized everyday objects’, such as physical stuff (his basic elements), artefacts (his considered view is that artefacts are not basic objects but we can set this to the side for now; they are useful illustrations, at any rate), and most importantly living beings such as plants, animals, and their parts are the most important, basic inhabitants of reality. By contrast, he thought that items such as features (being pale, weighing 80kg, sitting, walking, etc.), combinations between features and objects (my being sun-tanned, my weighing 80kg, etc.), statements, sentences, beliefs, and other mind-dependent items are not the most important or basic entities. He (again, I think, agreeing with common sense) took these latter to be genuine existents –hence my use of the term ‘entity’. He did not attempt to eliminate them from his inventory of the real world. But he thought that they somehow depend on the basic objects, and ultimately on living beings such as ourselves. Such basic objects, however, do not depend in a similar way on them. He calls a basic object an ‘ousia’, what we translate as ‘substance’. A non-basic entity is a being (‘on’ in Greek) but is not an ousia.

The second aspect of my aims in Priority in Aristotle’s Metaphysicswas to understand Aristotle’s view of what this dependence/independence relation consists in. He calls this relation ‘priority’, more specifically priority ‘in being’, ‘in substance’, or ‘in nature’. These terms suggest the notion of being first in a natural order or series. Let’s abbreviate this into ‘ontological priority’. An initial, natural interpretation of this idea is that while the prior items can exist without the posterior items, the posterior items cannot exist without the prior. The problem with this interpretation is that it does not work (I’ll explain why in reply to question 5 below). My suggestion was to start from Aristotle’s view of what entity is absolutely basic in reality and see what sort of relation of priority that entity could satisfy. Surprisingly, in his considered view, he thinks that the basic objects I mentioned earlier –living organisms such as plants, animals, etc.– are not absolutely basic. They are substances but they are so in virtue of being in a certain way, that is, because they have an essence or essential features. I am a substance, a particular human, but this is because of being a human, because of my human essence or nature, perhaps a certain sort of rationality or a certain sort of rational life. While this sort of entity is not an object –it does not, indeed cannot, exist by itself as a ‘free-floating’ thing without any actual humans– yet it is an entity, a being. More importantly, in Aristotle’s view, it is an absolutely basic entity as it makes objects, Aristotle’s substances, what they (essentially) are. The objects, however, do not, indeed cannot, make their essences what they are. This looks like a promising way to understand ontological priority: the idea is that it is the relation of making something what it (essentially) is. This is the route I followed in my book.

3:AM:You’re interested not only in understanding what Aristotle says but you also want to link it to contemporary discussions about substance, essentialism, modality, causation and explanation. Again, can you sketch what the key questions are that contemporary philosophers are wrestling with regarding these things?

MP:My approach to Ancient Philosophy, especially Aristotle and Plato, is to offer interpretations which are not only faithful to the texts but also charitable, coherent, and philosophically attractive –or at least not outright mistaken, outdated, or outlandish. I think that, while Aristotle’s views are interesting in their own right and historically, they can also contribute positively to contemporary philosophical debates: we can use them to undercut dilemmas in our current discussions, to diagnose what goes wrong in our formulations of philosophical questions, to discern and discard unattractive assumptions that escape our notice, and, more boldly, to offer solutions to problems. This applies not only to metaphysics or theoretical philosophy but also quite generally for any philosophical sub-discipline. It is an attitude that flourished in Oxford in the 20th century with thinkers such as J. Ackrill, D. Wiggins, G. Ryle, J. L. Austin, J. McDowell (see his commentary on Plato’s Theaetetus), and more recently David Charles. The latter called this approach ‘philosophical scholarship’. Not everyone in Oxford or indeed the Ancient Philosophical community is fond of this approach. I think, however, that it is immensely successful and fruitful.

Here are some examples of how this approach may be deployed in metaphysics. Contemporary metaphysicians still struggle with the distinction between substance and attribute, or the cognate distinction between particular and universal. Some thinkers have despaired with the sort of ‘object-first’ metaphysics that these distinctions presuppose and have argued that states of affairs, facts, or other similar items are basic. Others reject this roughly endurantist conceptual apparatus altogether, and argue in favour of perdurantist views in which objects are spatiotemporal worms, have temporal parts, and exist in four dimensions. Some of these more recent developments have seriously counterintuitive consequences. The Aristotelian approach, with its resources of substance, essence, and hylomorphism (the idea that objects are somehow matter—form compounds), can give far better results in the areas of identity, persistence, and individuation.

Related to this, Aristotle’s essentialism draws an important distinction between essential features, such as being a human or being a (Euclidean) triangle, and merely necessary but essence-based features, such as being capable of laughing or having a sum of interior angles equal to two right angles. Aristotle’s idea is that the latter, necessary features are derived from, explained, and somehow caused by the essence of the relevant objects. This idea gives rise to a powerful alternative to contemporary accounts of modality. In such accounts what makes true our modal claims –claims about what is necessarily, possibly, or actually the case– are states of affairs, facts, situations, or what have you in other possible worlds. Regardless of whether one follows a literal or non-literal interpretation of possible worlds, this view of modality is beset by serious problems. Aristotle’s focus on essence as explanatorily basic reverses our understanding of modality: it is not modal claims or modality that are deemed basic; rather the notion of essence, and claims about what is essentially the case, shed light on modality and ground modal claims.

Finally, in modern discussions of causation there is an obsession with a roughly Humean understanding of causes. This obsession has several aspects: an exclusive focus on efficient or moving causes (a billiard ball setting in motion another billiard ball); an ontology of events as causal relata (a ball’s hitting a window and a window’s breaking) and a suspicion against objects or properties as possible causal players; an emphasis on counterfactuals without a plausible or intuitive account of what makes them true; and a schism between causation and explanation. Aristotle is more flexible with his notion of causation: apart from efficient or moving causes, he also invokes material causes (what a physical object is made of or comes to be from), formal causes or essences (what makes something what it is), and final causes (what something is for, or what function or goal a being essentially has). This approach accommodates the intuitive idea that causation is intimately linked with explanation: a physical object’s constituents explain important aspects of its nature; a thing’s essence explains a thing’s identity, what it is, and why it has the necessary features it has or the attributes characteristic of it; a thing’s function or goal again explains why a thing is as it is (e.g., the function of sawing explains why we make saws in the way we do, with blades and teeth, and why we make them from the relevant materials). A further implication is that, in the Aristotelian view, an agent, say a human being like me or you, can straightforwardly be understood as a cause of, and so as responsible for, his/her actions: for an object or a person, too, can be a cause; there is no restriction of causes to events alone.

3:AM:Is the interest in Aristotle signalling a shift in contemporary metaphysicsaway from the ‘flat ontology’ of Quine to an ordered one? Is this a shift from ‘what exists’ to ‘what types of existent are fundamental’ and how are we to understand this distinction?

MP:It is true that thinkers such as Kit Fine, Kathrin Koslicki, Fabrice Correia, William Jaworksy, Michael Johnston, Michael Gorman, John Heil, Michael Loux, Tuomas Tahko, Michael Rea, Jonathan Schaffer, and so many others follow a roughly neo-Aristotelian approach to metaphysics. Whether this fact constitutes a shift away from Quinean views is less clear to me –there are definitely many important and celebrated philosophers working within a (broadly construed) Quinean paradigm. Jonathan Schaffer, in his well-known paper ‘On What Grounds What’, introduces the distinction between ‘flat’, ‘sorted’, and ‘ordered’ ontologies and argues for a view of grounding which favours an ordered ontology. The basic idea is simple. Quinean views aim at offering a simple and non-layered or non-hierarchical inventory of what exists. They are extremely restrictive in their ontology, often seeking to reduce what they take to be ontologically suspect to what they think are clear cases of existents. It is only these latter items which exist and have a place in their list of the inhabitants of reality. By contrast, an ordered ontology is more generous about what exists. Indeed, Schaffer goes as far as suggesting that everything exists: objects, attributes, events, facts, propositions, numbers, etc. The aim of this sort of ontology, however, is to specify what (sorts of) existents are fundamental, what are derivative, and to describe the relations of priority, grounding, dependence/independence, etc. that obtain among them. The picture of an ordered ontology is one in which the denizens of reality are organised in a roughly hierarchical order, with the basic entities at the privileged slot(s) of the hierarchy, and the derivative ones at lesser positions.

I think that this ordered picture is clearly Aristotelian in spirit: Aristotle himself did not invest any intellectual effort in reducing or eliminating items in favour of a very limited number of ‘select few’. Rather he thought that apart from his basic entities, substances and their essences, there also exist accidental compounds (a pale human), qualities (being pale), quantities (being two foot long), mental states (beliefs, ethical virtues), numbers, etc. At the same time, however, he argued that substances and ultimately their essences are fundamental, while other things depend on them by way of ontological posteriority. One notable difference from an overly generous ordered ontology is that Aristotle makes a distinction between existents which have essences and are worthy of scientific or philosophical investigation (eclipses, thunder, sleep, ethical virtues, artefacts, substances, etc.) and items which have names and accounts of what their names signify but do not exist, have no essences, and so are not scientifically explicable (goat-stags, centaurs, etc.).

3:AM:Is this part of the reason why you dispute the usual interpretation of Aristotle’s Metaphysics Δ.11, 1019a2-4, which takes it to be about priority in existence? Can you spell out the usual interpretation and then say how you interpret it?

MP:The main reasons for disputing the usual interpretation of that important passage are exegetical as well as conceptual. I think it would be a case of putting the cart before the horse if we approached this or other passages under the influence of a particular ontological theory (e.g., an ordered ontology) or a specific view of priority (e.g., a contemporary account of grounding).

In that passage Aristotle defines ontological priority as follows: an item is ontologically prior to another just in case the first can be without the second, while the second cannot be without the first. It is natural to understand this idea along the so-called ‘modal-existential’ lines: something is prior to another thing just in case the first can exist without the second but not the other way around. This construal is modal because it involves the ‘can’/‘cannot’, and so the notion of possibility or necessity depending on how one formulates the claim: while the prior item possibly exists without the posterior, the posterior is impossible to exist without the prior. Equivalently: while it is necessary that the prior item exists if the posterior exists, it is not necessary that the posterior exists if the prior exists. This construal is obviously also existential in that the relata are dependent/independent in respect of their existence.

Let us start with the exegetical problems this construal faces. Aristotle’s examples of prior and posterior items in this passage (but also elsewhere) cannot be good examples of ontological priority if this latter is understood modally-existentially. He claims that a substance, as a subject, i.e. a bearer of its attributes, is prior to its attributes (the passage doesn’t mention attributes as the posterior relata but it is natural to assume that they are intended as such). But just as attributes cannot exist without some substance or other (as their bearer), substances too cannot exist without some attributes or other to characterise them. For example, no human can exist without any complexion at all, just as complexions, too, cannot exist without some appropriate substance having a bodily surface. A second example is again a substance but this time as being prior to its matter. It doesn’t seem correct, however, that a human can exist without his/her body. Moreover, in an intuitive sense, a body can exist, say as a corpse, even if it is not a (living) human. Similarly, while Aristotle says that a whole is prior to one of its parts (or all its parts), we would think that a part or perhaps even all the parts of a whole can exist without the whole existing. For example, a brick can exist without the whole house existing; perhaps even all the building materials can exist (as, say, a pile of building materials in a construction site) without the house existing. So we need to modify or discard the modal-existential construal to make sense of these examples. Alternatively, we could think that Aristotle is confused or mistaken. But charity dictates that we should be more optimistic about his intellectual abilities!

The conceptual problems undermining the modal-existential construal of ontological priority have been rehearsed clearly and rigorously by Kit Fine in his famous paper ‘Ontological Dependence’ (there are cognate arguments in another well-known paper of his, ‘Essence and Modality’). Kit Fine criticises mainly the modal-existential view of ontological dependence or independence. But, insofar as ontological priority is a species of ontological dependence/independence, his arguments apply to priority too. That priority is a type of dependence/independence seems incontrovertible: it is just an asymmetric sort of dependence/independence. Asymmetry is a formal property of relations (for example, being the father of, being greater than, etc.): simply, asymmetry is what we describe when we say that something is prior to another thing but not the other way around; the clause ‘not the other way around’ captures the asymmetry of the relation of priority.

Kit Fine’s first criticism is that the notion of existence is in a way too strong and in another way too weak to capture what we understand when we think that an object ontologically depends on another. Existence is too weak because we may think that there is more to an object’s being than just its existence. In another way existence is too strong because an object’s being, in the sense of what that object is, need not include its existence.

His second criticism is rather devastating: it focuses on the modal aspect of the modal-existential construal. This aspect allows us to formulate priority claims as follows: x is prior to y just in case if y exists, necessarily x exists but not the other way around. One problem with this formulation is that it makes objects dependent on items we wouldn’t normally think they depend on; indeed, in such cases, we would expect the dependence to run in the opposite direction. For example, take Socrates and his singleton set {Socrates}. It seems true that if Socrates exists, then necessarily {Socrates} exists. But it makes no sense to think that Socrates depends for his being on his singleton set. In fact, we think that the singleton set depends on Socrates! Another problem is that anything you like or even all things taken together turn out to depend on any or every necessary existent or the universe as such if we assume that the latter must exist. If I exist, then necessarily the number 2 exists; or if I exist, then necessarily x = x; etc. etc. But it makes little sense to think that I depend for my being on numbers or on self-identity.

Kit Fine’s counter-examples to the modal aspect of the standard modal-existential view can be recast in a way that is more relevant to Aristotle’s views and examples. Take the case of substance as a subject or bearer of its attributes. The modal-existential construal effectively suggests that substance is prior to its attributes in that if some attribute(s) exist(s), then necessarily some or other substance exists. But, as noted earlier, it is also the case that if some substance(s) exist(s), then necessarily some or other attributes exist. This implies that we could not assert the ‘not conversely’ clause in the priority claim: it is not true, in this reading, that substance can be without its attributes but not conversely. There goes asymmetry, and with it there goes the priority of substance! A similar case can be constructed using Aristotle’s view that an essence, like being a human, is ontologically prior to matter, say a human body, and to particular substances such as concrete humans. Just as a body cannot exist (as, say, a living human body) or Socrates cannot exist (as a living human being) without having the essence being a human, similarly the human essence, being a human, cannot exist by itself without some body or other or some particular human or other in which or in whom to exist. In other cases, the modal-existential reading gives completely the opposite results to those Aristotle subscribes to. For instance, while he argues that particular substances such as Socrates or Bucephalus are prior to species such as human or horse the modal-existential reading requires a reversal of this claim: for if Socrates exists, then necessarily the species human exists; but it is not true that if the species human exists, then necessarily Socrates exists. So, contrary to his considered view, the species would prove prior to the particular substance!

My suggested interpretation rejects the modal-existential construal in favour of an essentialist reading of the priority claims. What this means in the narrow context of the passage we’re discussing is that we should read Aristotle as saying that a thing is ontologically prior to another just in case the first can be what it (essentially) is without the second, while the second cannot be what it (essentially) is without the first. There is nothing extravagant in this reading. The verb ‘to be’ in Greek can be read as complete (and so as existential, in the way the modal-existential construal reads it): ‘x is’ in the sense that ‘x exists’. But it can also be read as incomplete and elliptical: ‘x is’ in the sense of ‘x is something or other’ or ‘x is thus-and-so’. This latter usage of ‘to be’ can be either predicative, as in ‘Socrates is pale’, or essential, as in ‘Socrates is a human’. So there is a natural way to get the essentialist reading I am aiming at. Moreover, it is important to remember that what I’ve abbreviated as ‘ontological’ priority Aristotle labels as priority ‘in substance’ or ‘in nature’. These characterisations clearly have essentialist connotations: ‘substance’ can be understood as ‘substance of’, indicating the essence of a thing, whereas ‘nature’ is normally understood as ‘nature of’ and clearly picks out a thing’s essence. In this context, both ‘substance of’ and ‘nature of’ would imply the dependence of a thing on its essence or the priority of the essence over the relevant thing.

The second move of my interpretation is to argue that the presence of ‘can’ or ‘cannot’ in Aristotle’s formula does not require that modality (possibility or necessity) is a basic part of his considered account of ontological priority. Rather, I take it that modal claims follow from, and are in some sense grounded in, essentialist claims. For example, because every (Euclidean) triangle is essentially a three-angled closed plane figure, it necessarily has a sum of interior angles equal to two right angles. Because every human is essentially rational, every human necessarily has the capacity to laugh. How does this apply to ontological priority? The basic priority claim is that a thing is ontologically prior to another just in case the first makes the second what it (essentially) is, but not conversely. While there is no mention of ‘can’ or ‘cannot’ in this formula, yet it follows from it that the first item can be what it essentially is without the second (for the second does not make the first what it is), but the second cannot be what it is without the first (as the first makes the second what it is).

To flesh out the bare bones of this interpretation, let us take some of Aristotle’s examples. A particular substance, as a subject or bearer of its attributes, is prior to its attributes in that what it is to be a specific attribute consists in its belonging to some or other particular substance of an appropriate type. For example, the essence of the quality being red is to be a colour quality of a specific type belonging to some or other bodily surface (as its subject). Such a surface, in turn, belongs to some or other particular physical substance (as its subject). It is not true, by contrast, that to be a specific (type of) particular substance consists in its belonging to some or other attribute. Another example is the essence (or form) as being prior to particular substances having that essence or to the matter of such substances. Being a human (the essence) is prior to any and every particular human in that being a human makes any human what he/she is but the converse is not the case. Being a human is prior to any and every human body (the matter) as being a human makes the relevant bodies what they are –functional, living human bodies– but not the other way around. This interpretation, then, seems not only to accommodate Aristotle’s examples but also to overcome the conceptual difficulties raised against the modal-existential construal.

3:AM:So how does priority function in Aristotle’s system? And is it only in his Metaphysicsthat it’s relevant or do we find it elsewhere, for instance, in his Ethics?

MP:In answering this question I cannot help but paraphrase Jonathan Barnes’s joke about Ancient Logic lacking sex appeal: ‘Priority lacks sex appeal’! But just as I disagree with the spirit of Barnes’s joke about Ancient Logic, similarly –and more vehemently– I disagree with its priority-related paraphrase. As I alluded earlier, several modern metaphysicians use Aristotelianconcepts, including priority, to address contemporary questions. Regardless of this diachronic, as it were, sex appeal, it would also be a mistake to think that, within Aristotle’s philosophy itself or for that matter Aristotelian scholarship, priority has only a narrow application to, or is only of interest for, metaphysics.

Ontological priority, as I understand it, is important in Aristotle’s metaphysics as a criterion for what counts as a primary substance. To put this in terms of the earlier point about ordered ontologies, ontological priority would codify the relations between the fundamental and the derivative denizens of reality and would pick out the absolutely basic entities. It would give us the ontological hierarchy and would specify what sorts of existent are placed in each of its slots. If I am right, this can be illustrated as follows. Starting from entities such as (for example) accidental compounds –a pale human– we would be able to see how they are ontologically posterior to entities such as being pale and some or other particular human. For what it is to be a pale human is for the complexion being pale to belong to some bodily surface of some or other particular human (but not the other way around). Now take being pale: its essence consists in its being a specific type of complexion belonging to some particular bodily surface or other as its subject, and ultimately to some or other particular substance (which serves as the subject or bearer of a bodily surface). Some interpreters think that this is where we reach the bedrock of Aristotle’s ontology: impressed by his claim in the Categories that particular substances are primary substances, they conclude that nothing else is prior to them. But they are not sensitive to Aristotle’s justification for this claim: particular substances are primary as subjects or metaphysical bearers of non-substance attributes. This raises the question of whether they are such subjects or bearers in their own right or whether there is anything which accounts for their status as such.

The Categories only alludes to the idea that there is something prior to them in virtue of which they are subjects: their what-it-is, presumably understood as the essence of their respective species. In other works, however, such as the Physics, his scientific works, the De Anima, and the Metaphysics Aristotle invokes his hylomorphic picture. This entails, first, that particular substances are analysable into matter and form, where form is identified with their essence. Second, what accounts for the being of particular substances, as well as their matter, and what grounds their status as metaphysical subjects or bearers of properties –simply what makes them the familiar (types of) objects they are– is their essence or form. If this is correct, what we find at the most privileged slot of Aristotle’s ontological hierarchy, are the essences or forms of particular substances and their matter, those entities in virtue of which substances and matter are what they are. (This picture is accurate insofar as the physical, perceptible, and changeable reality is concerned. I am not here going into Aristotle’s theology, the exalted being of his divine intellects, or the absolute and ultimate primacy of his prime mover, for this would open a different can of worms!)

Ontological priority, however, is also important for other areas of his philosophy. So is priority generally speaking. To be clear, Aristotle distinguishes several types of priority: in time, in order, in value, in potency, in knowledge, in definition. Some of them can be systematically linked to ontological priority in a substantive way: for example, what is prior in knowledge is what defines other things but is not defined by them, whereas what defines things is what makes them what they are, their essence. Other types of priority bear only an abstract resemblance to ontological priority in the sense that there is a general description which covers both them and ontological priority. This general description may be something like ‘x’s being without y in some respect or other but not conversely’.

To complicate things, Aristotle sometimes speaks of priority in being or substance in the sense of ‘not reciprocating as to implication of being’. This is not a weighty essentialist notion but a rather logical relation of something’s implying or entailing something else but not conversely. For instance, being a human entails being an animal but not the other way around; there being two objects entails there being one object but not the other way around. It may be that some recalcitrant cases of priority in being or substance are to be read in this thin way. For example, he thinks that ‘topical’ matter (the matter underlying locomotion) is prior to the other types of matter: matter for qualitative, quantitative, and substantial changes. An innocuous way to spell this out is to think that if there is matter for substantial change (the coming-to-be or passing-away of a physical object), it follows that there is matter for change in quality, quantity, or/and location. By contrast, if there is matter for locomotion, it is not necessary that there be any other sort of matter. This may also help explicate his difficult claim that locomotion is prior in being or substance to other types of change: if there is (a capacity for) qualitative, quantitative, or/and substantial change, then there must be (a capacity for) locomotion. But the converse does not hold good. Why Aristotle shifts to this thinner, logical or entailment-based, notion of priority may have to do with the fact that in such contexts he does not discuss what is ontologically fundamental –his cases of primary substance– but derivative types of entity, such as matter or change.

Outside his theoretical philosophy Aristotle deploys ontological priority or cognate dependence and independence relations in several areas. It is worth mentioning just two cases, one ethical and one political. In his Nicomachean Ethics he takes decision or choice (prohairesis) and a virtuous state of character to be prior to a virtuous action in the sense of determining the ethical quality of an action. At the same time, practising in virtuous activity seems prior to a virtuous character in that it makes us acquire and consolidate such a character. Another ethical example is that of the intellectual excellence of wisdom and its respective activity, theoretical contemplation: theoretical wisdom is prior to the practical intellectual excellence of phronêsis (sometimes translated as ‘prudence’ sometimes as ‘practical wisdom’); and the exercise of wisdom, the activity of theoretical contemplation, is thought to be prior to any practical intellectual or virtuous activity. The political example comes from his Politics, where he argues that the political community or the state is prior in nature to the individual citizen. It seems plausible to understand this claim in the essentialist way: what makes an individual member of a society a citizen of a certain sort is the type of political community, state, or constitution he/she is a member of, but not the other way around.

3:AM:In Aristotle we have objects and modes of being, which includes essences. Can you say how we’re to understand these, and why they are not linguistic or conceptual formulae, abstractions in thought, fictions, or constructs?

MP:This is a controversial interpretation I propose in my work to understand Aristotle’s basic ontological distinctions and claims. There are allusions to this interpretation in the work of Michael Loux. David Charles, too, agrees with me on this interpretation. The starting-point is simple. There is a fundamental categorial distinction between entities such as Socrates (a particular human) or Bucephalus (a particular horse), entities such as human or horse (the species or the universal type), and entities such as being a human or being a horse (the essence of humans and horses respectively). It seems plausible to think that particular objects and their types are cognate. One consideration is linguistic or grammatical: such entities seem to be the referents of the subject-terms of well-formed sentences. ‘Socrates is pale’; ‘this particular human is running’; ‘human [the type] is [definitionally] rational biped animal’; ‘every human is capable of laughing’. Another consideration would be to think that types are ontologically parasitic on their tokens, and species or kinds on their members. The species human is somehow reduced to the class of humans. My view need not be committed to this last idea. But the intuition I am driving at is that entities such as Socrates, this particular horse, or the type oak-tree seem to operate as objects, particular or universal objects as the case may be. The same idea can be applied to Aristotle’s material items: just as there is this particular human body, similarly there is the type human body. And they, too, seem to be particular or universal objects: this particular bodily object or the general type of body.

It does not make sense, by contrast, to think that entities such as being a human or being a horse –Aristotle’s essences or forms– are particular objects or types of object. First, they don’t have the right logical form to be objects: they don’t seem to correspond to referents of subject-terms but to whatever predicates pick out. In more precise, Fregean terms, they are the ontological correlates of open sentences or non-saturated predicates: ‘__ is a human’; ‘... is a horse’. A further reason for distinguishing them from particular objects (or token-objects) and universal objects (or type-objects) is that insofar as they are essences such entities are prior to particular or universal objects. This is where ontological priority as I understand it is useful. Being a human is prior to particular humans in that it makes them what they are but not conversely. Being a horse is prior to the type horse in that what it is to be the type horse is to be of the equine essence (alternatively: what it is to be of the type horse is to be a member of a type of thing having the essence being a horse). This sort of ontological priority, however, is incompatible with strictly identifying objects with their essences. As noted earlier, priority is an asymmetric relation (remember: ‘but not conversely’), whereas identity is a symmetric relation: if Socrates = Plato’s teacher, then Plato’s teacher = Socrates. No relation can be both asymmetric and symmetric. So if our understanding of an essence as ontologically prior to the objects having that essence is sound, we have to distinguish between essences and the relevant objects. That our understanding of essence is sound seems incontrovertible: for essences are introduced precisely to serve as the ontologically fundamental, prior, or primary entities.

Is there any evidence for this line of thought in Aristotle? I think so. First, Aristotle uses the technical term ‘what-it-is-to-be’ to describe essences. It is natural to think that what in reality is picked out by such a phrase are entities such being a human, or to be a horse, or what-it-is-to-be an oak tree. And these entities are not objects or types of object but are ways or modes of being. At any rate, they are cognate with property- or attribute-like entities. Moreover, he often talks of essence as ‘what-it-is-to-be for a (type) of object to be’. This also suggests that essences are not themselves (types of) objects. Rather, they are how (types of) objects are –ways or modes of being for such objects. However, it is important to point out, as you do in your question, that ways or modes of being as such need not be essential ways of being. There are ways of being which are not essential but merely necessary or even accidental. For example, being wise is a way of being for Socrates but is not essential to him. Aristotle himself points out that the thing which is pale (say, Socrates) is not the same as being pale. This supports my non-identity reading of (type of) object versus way of being. It does not entail, though, that being pale (for example) is the essence of Socrates.

There is even more important evidence in favour of this reading. At crucial junctures of his Metaphysics, Aristotle holds that Human (the type) is not the same as being human/being a human soul, while Soul is the same as being a soul.

The first statement suggests that a particular object that is a human, say Socrates, or the type human just is not the same as its essence. The second implies that soul, an item which Aristotle takes to be the paradigmatic instance of an essence (in the case of living beings), is identical with its own essence, being a soul. But being a soul seems to be a way of being. So essence seems to be a way of being, not identifiable with a (type of) object.

There is another important problem, which you also raise in your question. We may accept that essences are not objects. We may even concede that they could be understood as ways of being. Why, however, do we have to say that they are real-world items, entities, as I argue in my work? Why can’t they be merely linguistic items, verbal definitions, abstractions in thought, fictions, or what have you? The reason for following the ‘real-world’ route is mainly exegetical. Aristotle seems to be a realist: he thinks that essences are items which are captured by but are not the same as definitional statements: ‘definitions are accounts of essences’. So while essences are mirrored in language, they are not themselves just a piece of language or merely conceptual. To be clear: there are interpreters who prefer a different, nominalist reading of these claims. But I think that they cannot explain away Aristotle’s strong realist inclinations and arguments.

Generally, Aristotle’s interest in definition as an account of the essence suggests that he is not seeking simply verbal definitions or dictionary entries. Rather, just as Plato before him, he is interested in definitions that describe real-world items (not words) in terms of their real natures. This is so despite the fact that he also thinks that there is a type of definition which is simply verbal (or ‘nominal’ as it came to be called): an account of what a term or similar phrase signifies. For he thinks that this sort of definition is, at most, a starting-point for further inquiry into the proper, scientific or scientific-like, definition of a real entity. To use a modern example, while he agrees that there are ‘semantic’, as it were, definitions such as ‘water is a colourless, potable liquid filling our lakes and rivers’ (or something along these lines), in his scientific and metaphysical inquiries he seeks more substantive definitions such as ‘water is H2O’.

Another reason for favouring my reading is philosophical: the right sort of realism might seem more attractive than its alternatives. My reading of Aristotle does not saddle him with a Platonist ontology: understood as ways of being, essences are not transcendent Platonist Forms but are ways of being for objects and so cannot exist without any objects at all. They are not ‘free-floating’ existents, to use a metaphor I invoked earlier. On the other hand, the advantage over nominalist views which deem essences merely linguistic items or abstractions we ourselves create in our thought might be that my realist reading avoids the possible charge that essences are simply our own arbitrary, conventional, or pragmatic ways of categorising, understanding, or describing things.

3:AM:You argue that essences have their own essences. How come an object is not the same as its essence, but an essence is thought of as the same as its essence? This looks inconsistent.

MP:This issue follows on naturally from the previous question. Remember Aristotle’s two statements I just mentioned:
Socrates/the human type is not the same as being a human (the essence).
Soul (an essence) is the same as being a soul (an essence).
Aristotle, then, thinks that essences have essences. This is the flipside of his view that essences, as primary substances, must be definable. Definitions are just accounts of essences. But there are two problems here. First, as you are wondering, why differentiate between the essences of (types of) objects and the essences of essences? Shouldn’t we think that what applies to the one case should apply equally to the other? The second problem is more serious. There is an air of paradox in the locutions ‘an essence of an essence’ or ‘a definition of a definition’. An essence is of (types of) objects, full-stop. A definition is of a definable item, full-stop. Why invoke essences of essences or definitions of definitions? Moreover, doesn’t this view generate an infinite regress? If there is an essence of the essence being a human, then why stop there? Why isn’t there also an essence of the essence of the essence, and so on and so forth ad infinitum?

I’ve explained why (types of) objects are not the same as their essences in terms of the categorial distinction between (type of) object and way of being. But why think, by contrast to this non-sameness claim, that essences are the same as their essences? My suggestion is that in this last case we are misled by our usual phraseology. While we say that essences ‘have’ essences or that there are essences ‘of’ essences, we should not think that essences are made what they are by distinct, prior items, over and above themselves. Nor should we suppose that there are separate or more basic entities than essences, their ‘super-essences’, that make them what they are. Rather, when we give a definition of (say) being a human as being a rational soul, thereby describing the essence ‘of’ the essence being a human, we are just unpacking what that essence is the same as –just that very essence itself. We are not bringing in a further, prior entity; we are just ‘decompressing’, as it were, the very essence that being a human consists in or is identical with. This approach can of course block the infinite regress: since there is no extra entity, we don’t need an extra essence to account for it. Of course we may find the description ‘being a rational soul’ conceptually more intelligible or clarificatory than ‘being a human soul’. But this is just an epistemic point; it cannot underwrite the introduction of an extra, more basic entity than being a human.

The last question here is why we should agree with Aristotle that essences ‘have’ essences they are identical with, or equivalently that there are definitions ‘of’ essences unpacking their very own content? As implied earlier, Aristotle thinks that a basic requirement for something to count as a primary substance, a fundamental entity, is that it be knowable. Part of the reason for this idea is that a fundamental entity should enable us to know all other entities which depend on it. But how could it serve this role if it is itself unknowable? Hence, it must be knowable. But for an entity to be knowable, Aristotle plausibly thinks, is for it to be definable: we know it properly just in case we can define it. This entails that if essences are fundamental, they must be knowable and so definable. Aristotle wishes to avoid the view that his fundamental entities turn out to be indefinable and unknowable mereological atoms of some sort.

3:AM:Why is it important to your account to set out the differences between two kinds of matter? What apparent conflict is overcome if you do this?

MP:There is a fundamental problem in Aristotle’s hylomorphism. He thinks that objects are compounds of matter and form. They are somehow analysable into or consist of matter and form. He also identifies form with essence. For example: I am a substance, a living being, but I am made of matter, my body, plus form, the human essence, something like being a rational soul or living a certain sort of rational life. Further, he argues that form is ontologically prior to compounds as well as their matter. In my view, this entails that the form being a human makes not only me and other humans what we are but also makes my body and other human bodies what they are. The converse just isn’t the case.

At the same time, however, several of his arguments and examples imply that the form itself is dependent on matter in a variety of important ways. It is incontrovertible that, in Aristotle’s view, a form cannot exist without some or other appropriate matter. But his arguments seem to suggest that matter is not simply a necessary condition for a form’s existence. Rather, matter seems to be an essential part of what a form is. If we were to define a form correctly, i.e. in a way that truly describes the essence it is, we would have to mention matter of a certain sort. An illustration Aristotle himself offers comes from the case of a phoneme (a ‘syllable’, as he calls it) and its form. What it is to be the phoneme ‘BA’ is not simply a formal item, a structure, shape, configuration, or arrangement. Rather, its form is a certain arrangement of a ‘B’ before an ‘A’. If, as Aristotle thinks, ‘B’ and ‘A’ are analogous to matter or material parts, this suggests that the form itself essentially involves matter or material parts. Take the human case again: it would be odd to insist that we could correctly define the essence or form, being a human, without any mention at all of an appropriate type of living body or its structure. If we attempted such a ‘pure’, matter-free definition, we might end up with something like ‘being a certain type of rational soul’. But why not think that this type of rational soul is something that is not characteristic of just humans but also covers disembodied divine intellects? If this were the case, our definition would be incorrect.

So here is the conflict you allude to in your question. Aristotle seems to think that a form is essentially matter-involving. At the same time, however, he holds that it is ontologically prior to matter (i.e., a form’s essence does not include any matter, whereas matter’s essence is fixed by the form). In my work I argue that this inconsistency is only apparent. To develop this argument, first we have to invoke the distinction I introduced earlier (in reply to your question 7) between objects or types of object, on the one hand, and ways of being, on the other. A simple way to defuse the apparent inconsistency is to think that the matter which is ontologically posterior to form, that which depends on form for its being, is an object- or type-object matter. What the human form determines is the nature of my particular human body, an object-matter. Similarly, the human form fixes the nature of the type of body involved in the human kind: this is a kind of matter, a type-object. By contrast, the matter involved in a form’s own essence is not an object or a type-object. Rather, it is a material way of being: how a material object or type-object essentially is –for example, being a human body; or consisting of certain bodily parts. This is as it should be: for the form itself is neither an object nor a type-object. Rather, it is an essential way of being for objects or types of object. Hence, its essence should consist in or be identical with a way of being. My view entails that this way of being is complex and includes not only formal but also material ways of being as its constituents. If this is correct, there is no inconsistency. The form is ontologically prior to object or type-object matter but is not (indeed cannot be) ontologically prior to the material ways of being essential to it.

I should point out that this is a controversial interpretation of Aristotle’s hylomorphism. It may be helpful to mention some different approaches. Most interpreters take Aristotelian form to be essentially pure or immaterial. And they think that when Aristotle argues for an intimate dependence of form upon matter he has in mind its merely necessary dependence on matter for its existence: while a form is essentially matter-less, it cannot exist without matter. Another way in which these purist theorists develop their view is by insisting that while a form’s definition does not mention any matter, yet it contains items which entail that it could not exist without any matter, perhaps even that it could not exist without a specific range of types of matter. I’ve raised a lot of objections to this interpretation. A central question is this: how can a definition necessarily entail certain types of material item without itself using material terms or referring to material entities? Insisting that there is just no mention of matter in a form’s definition looks a lot like Basil Fawlty’s manic line ‘Just don’t mention the war!’.

Another interpretative approach which seeks to overcome the inconsistency I just outlined (form is prior to matter and form depends on matter) is to give up altogether on the ontological priority of form over matter and compounds. In this view, what is ontologically basic is the compound: particular humans, horses, or oak-trees. Matter and form, by contrast, are not ontologically basic but are just theoretical posits or abstractions in thought generated from the compound. The only type of priority that the form enjoys over matter and compound, in this view, is of a definitional and epistemic sort: the definition of matter and the compound is framed in terms of form but not the other way around. I’ve labelled this interpretation ‘Compound First’ view. One of the main objections to it is exegetical: Aristotle claims that form is the primary substance. It is not simply epistemically or definitionally but also, and more importantly, ontologically prior to matter and the compound.

My view is strongly opposed to purist and compound-first views. I’ve called my interpretation ‘Impurism’ or, more figuratively, ‘True Grit’! The idea is that form ‘has true grit’ as it essentially involves matter of a certain sort and so is definable in terms of matter.

This view, of course, has its own difficulties. Here are three:
(a) Does it end up making the form ontologically posterior to matter? If a form’s essence includes material ways of being, don’t the latter prove prior to the former?
No. As I implied earlier, the essence that a form consists in is complex and involves not only material but also formal ways of being. Let’s take Aristotle’s pet illustration of a hylomorphic compound, the snub nose. The form of this compound is being snub or snubness. He clearly thinks that this sort of form is definable as follows:
Being snub =def being nasally concave (or equivalently: being concavely nasal).
In this definition we get a glimpse of what a form consists in or is identical with. It is a way of being –being snub, being nasally concave, etc. Moreover, it involves a formal way of being, the ‘shapy’, form-like feature of being concave. In addition, however, it also includes a material way of being, being nasal or being nasally fleshy or what have you. This suggests that a form is not ontologically posterior to matter. Rather, it is essentially a form-cum-matter involving entity. Further, there is nothing in it which could threaten to transform it, as it were, into anything other than an essential way of being for (types of) objects. Hence, it is just a form or essence but it includes not only ‘pure’ but also ‘gritty’ items.

Another point arising from the snubness case is that Aristotle argues (or so I interpret him) that the items within a form’s essence –say, being nasal and being concave, in the present case– are not independent conjuncts that somehow come together and define the form by intersection or overlap. Being nasal and being concave are not self-subsistent, ‘objectual’ (as I call them) parts of the form in any strong sense of parthood. Rather, they are just aspectual ‘parts’ of it, so not really parts at all. Aristotle thinks that the formal and material items within a form’s essence are essentially interdependent, inextricable ways of being, neither of which is prior to the other. This is why I used either ‘being nasally concave’ or ‘being concavely nasal’ to emphasise this no-priority idea. The form, then, consists in or is identical with this inextricably interwoven material-cum-formal way of being.

(b) How to specify the matter which is essential to form or how to distinguish it from the matter which belongs only to particular objects or type-objects?
So far I’ve used mainly schematic examples: while the form is prior to this particular human body or to the type human body, it essentially involves a material way of being such as having a human body. But this is not informative. And it also seems circular: ‘human’ is used in the specification of the form being a human.

One suggestion would be to insist that the only difference is that between object (or type-object) and way of being. Whatever material item is essential to the particular or general compound object is also what we find in the essence or form, albeit in the guise of a material way of being. Suppose that bones, flesh, muscles, and tissues of a certain type and arrangement are essential to particular humans and the kind human. This view would entail that the matter which is essential to the human form is just being made of bones, flesh, muscles, and tissues of that type and arrangement. Again this may seem uninformative and unsatisfactory.

Another suggestion would be to hold that the form involves a disjunction of the possible material items and characteristics that a particular or general compound may have. For example, while this particular human has blue eyes, the human form would essentially involve (inter alia) having eyes of either blue or black or green or brown or... colour. This solution is problematic, for Aristotle thinks that forms are not only unifiers but also themselves paradigmatic unities. Not only do they make particular and general compounds unified objects or types of object. They also are fundamental unities in their own right: they are not made one in virtue of anything extrinsic to them. But if so, how can a form be one or make anything a unity if it is of a disjunctive nature?

It would also be a non-starter for the ‘True Grit’ theorist to maintain that the material way of being internal to form is to be specified as being material in a way appropriate to embody the relevant form. For this would effectively reduce the matter in question to form. Hence, the view would not be ‘gritty’ at all. Rather, it would collapse into some form of purism.

It seems more promising to argue that the ‘matter in the form’ is to be understood as a generic but sufficiently unified material way of being. Take one of Aristotle’s celebrated artefact examples: a saw. The form of this type of compound is something like the function of being capable to cut in a specific way. True grit would understand this form as essentially matter-involving. But it would not specify this matter as being made of either iron or bronze or steel or... Rather it would specify it as being made of hard, non-brittle, etc. metal. This is more attractive. Yet it raises further questions. Can’t we also make saws from non-metals, such as diamond? And how do we even begin to specify the material ways of being essential to the forms of more complex compounds, such as living beings, Aristotle’s paradigmatic substances? There is a lot of work to be done in this area. But it would be helpful to point out that this work is not of the ‘armchair theorising’ variety. This should also be clear in the light of my earlier points about Aristotle’s interest in definition. It is actual scientific inquiry which will enable us to discover the correct specification of forms, including both their formal and their material aspects. Similarly, to get clearer about his view we have to study more carefully his scientific treatises.

(c) To close this discussion it is useful to anticipate a common source of incredulity toward ‘True Grit’. The typical reaction of a theorist or interpreter who encounters this view is to think that including matter in the form would turn a non-material entity, a form, into a material object. Moreover, they reason, since a form is what we grasp when we grasp the definitions of things, enmattered forms would (per absurdum) smuggle material bits into our minds or/and our heads. In the same vein, wouldn’t a compound made of (for instance) metal with a matter-involving form end up having double the metal and so double the weight it has?

These are not serious worries once we draw clearly the distinction between object (whether particular or general) and way of being for an object. A form includes material ways of being, not material objects or bits. It is not made of (e.g.) metal; rather, it involves items such as being metallic. As for the issue of matter in our minds or heads: engineers and material scientists study matter and its properties very successfully using not only mathematical formulae but also accurate qualitative descriptions. None of them has ever complained of having material bits in their mind or head as a result of understanding their subject-matter.

3:AM:Why is it important that material and change-related features are parts of a form’s essence, without either having priority over the other?

MP:This question follows on naturally from the previous one. I already explained the point about ‘no priority’ in my answer to that question. The idea is that, in Aristotle’s view (at least as I understand him), a form’s definable essence does not include any items which are independent conjuncts or self-standing entities. Rather, the ways of being the form consists in are essentially interdependent, separately incomplete, and jointly identical with that form. If an item within a form were prior to the rest, it would be responsible for the being of the rest. But if so, it would be prior to the form too. This would generate an infinite regress. Moreover, such a prior, self-standing entity would also undercut the unity of the form: for the form would be one not in its own right but in virtue of that separate, prior entity. Aristotle’s essential interdependence view (the ‘no priority’ point) overcomes both of these problems neatly.

The other, more important part of this question is about the role that material and change-related ways of being serve within a form’s essence. I’ve touched on some of the exegetical reasons why material items are important and should be included in the form in my reply to question 9. But it would be helpful to offer a more general argument that covers change-related features too. First, let me clarify what I mean by ‘change-related’ features. Suppose we are seeking to define the essence or form of humans. Apart from formal items such as being a rational soul or living a certain type of rational life or material items such as being made of flesh, bones, muscles, and tissues of a certain type, this essence should also include items such as being capable to move our bodies, to perceive, to ingest and digest nutrients, to reproduce, to gain knowledge, etc. It seems clear that such features consist in capacities to cause or undergo changes –in a broad sense of ‘change’. It is such features or ways of being, then, that I refer to as ‘change-related’.

Why should such items, as well as material ways of being, be included in a form? To answer this question, we have to keep in mind that we are interested in natural forms, that is to say, forms of natural beings or compounds. We are not asking what is involved in the essences of abstract entities (such as mathematical objects). Nor are we inquiring into the essences of immaterial, divine entities. Natural objects are, in Aristotle’s view, perceptible, material, and changeable. In fact, he thinks that they have an internal principle of change and rest and identifies this principle with matter and form. Importantly, natural objects have certain material and change-related features necessarily. For example, while it is contingent whether a human has blue or brown or... eyes or whether he or she learns how to speak a foreign language, it is necessary that he or she has specific types of sense organ, such as eyes with some or other colour, or that he or she can learn things. Moreover, Aristotle contends, such necessary characteristics of natural matter—form compounds are grounded in, and so are explained on the basis of, their essence or form. It is in virtue of the form being a rational soul that humans necessarily have the capacity to learn or laugh. A mathematical parallel used heavily by Aristotle (which I also mentioned earlier) may be helpful here: while all (Euclidean) triangles necessarily have a sum of interior angles equal to two right angles, this necessary feature is not part of the essence of being a triangle. Rather, being a triangle is to be a closed, three-angled, plane figure. But this essence grounds and explains (note that this relation is far stronger than mere logical implication) that necessary feature. Indeed, we can grasp how this grounding and explanation work by grasping the relevant geometrical proof.

Against this background, I argue that an Aristotelian natural form must essentially include material and change-related ways of being if it is to ground and explain the necessary materiality and changeability of the compounds it is the essence of. How could a saw’s form ground necessary features of saws such as (for example) having teeth and a blade or being metallic or the capacity to cut hard materials, if it were specified in a pure, matter- and change-free way? If one defined a saw’s form as simply the capacity to cut or divide, one’s definition would be consistent with the capacity of geometrical lines to divide geometrical angles. But it seems absurd to adopt a definition of a saw which could also apply to geometrical lines! Another example: if the essence or form of a human were simply to be a rational soul, how could it ground or explain necessary features of humans such as having bodily extremities, being able to wield tools, being able to walk, etc. Why not think that this sort of pure, matter-less, and change-less form also covers disembodied, unmoved, and asocial intellects?

Aristotle himself rehearses a similar argument in his demarcation of natural and mathematical sciences (in PhysicsII.2). He maintains that mathematicians are correct in defining mathematical objects and their essences without mentioning any matter or change. This is because such items are indeed essentially independent of matter and change. No error arises, then, in our mathematical reasoning, proofs, or explanations from assuming as starting-points such matter-less and change-free definitions. By contrast, if we define natural compounds and their forms without mentioning matter or change, our definitions will be incorrect and will yield errors in our inquiries into natural science. Let’s take the snubness case again (as indeed Aristotle does in that chapter). One type of error would be exemplified by defining snubness simply as geometrical concavity: this is patently false as snub noses are not geometrical concavities. Another type of error, cognate with the point I just made about grounding and explanation, is that even if we define snubness as a geometrical concavity in a nose, we may mistakenly infer from this that snub noses are changeless or stable in the manner of geometrical objects. But if so, how could that purist definition ground and explain the necessary capacity of snub noses to lose and regain their shape (perhaps due to pressure exerted temporarily by a punch)?

3:AM: Is his causal-explanatory model of essence and definition applicable to substance-kinds as well?

MP:I think so, and I’ve argued the case in several places. First, however, let me outline the causal-explanatory model –CEM for brevity. In book II of his Posterior Analytics Aristotle discusses scientific inquiry. He approaches this issue on the basis of what he takes as the four basic questions we may inquire into:
(a) Is an F (a) G?
(b) Why is an F (a) G?
(c) Does X exist?
(d) What is X?
I have presented his questions in a way which is more accessible to a modern reader. Some examples would help clarify the general picture. In asking an (a)-type question we are asking whether the moon suffers light-loss (in the case of a lunar eclipse); or whether the clouds are noisy in a certain way (in the case of thunder); or whether broad-leafed plants are deciduous (in the case of leaf-shedding). In asking the ‘why?’ question (b) we inquire into why the moon suffers light-loss, why the clouds are noisy in a certain way, or why broad-leafed plants are deciduous. On the other hand, the existence question (c) is illustrated by ‘does lunar eclipse exist?’, ‘does thunder exist?’, or ‘does leaf-shedding exist?’ And the ‘essence’ or ‘what is it?’ question (d) concerns what lunar eclipse is, what thunder is, or what leaf-shedding is.

Two points are important here. First, while the Posterior Analytics occasionally gives examples of scientific questions about substance-kinds (such as god, human, or soul), it never develops any of those examples. Nor does it show how CEM applies to them. Rather, this treatise focuses exclusively on cases of types of process such as those I’ve just offered. Second, Aristotle argues that these four questions are not disparate but are systematically interconnected. At the level of scientific progress, as it were, once we know that the clouds are noisy in a certain way (an affirmative answer to an (a)-type question), we inquire into why the clouds are noisy in this way (b). Similarly, once we grasp the existence of thunder (perhaps on the basis of reliable observations) and have an affirmative answer to a (c)-type question, we investigate what thunder is (d). More importantly, Aristotle holds that our grasp of the ‘fact’ question (a) is effectively the same as that of the existence question (c): to know that the clouds are noisy in the relevant way is to know that thunder exists. This is because our pre-scientific understanding of the phenomenon of thunder relies on our definition of the term ‘thunder’: since in our common-sense conception ‘thunder’ signifies the same as ‘a type of noise in the clouds’, our knowing that the clouds are noisy in a certain way just is to know that thunder exists. Furthermore, our grip on the ‘why?’ question is the same as our knowledge of the ‘what is it?’ question. Knowing why the clouds are noisy in that way is to know what thunder is. Aristotle offers as a putative answer the ‘quenching of fire in the clouds’, which doesn’t seem to be his official account of this meteorological phenomenon. At any rate, we can use this as a working example.

So far I’ve analysed the interconnections among the questions of scientific inquiry only in epistemic terms: our knowledge or understanding of facts, causes, existence, and essence. But Aristotle’s CEM is not just about our knowledge, interests, or pragmatic concerns. He contends that there is a strong interdependence or even sameness between fact and existence and, more importantly, an interdependence or sameness between cause and essence. This is a metaphysical, not simply an epistemic, thesis. Let’s take the second interdependence or sameness, which is crucial to our concerns. The idea is that the cause of a phenomenon –in the present case, the quenching of fire which brings on noise in the clouds– just is (in some way) the fundamental essence of the relevant phenomenon, what fixes the identity of thunder. Quenching of fire in the clouds brings on noise in the clouds. And to be thunder is just to be a noise in the clouds brought on by fire quenching. Conversely, too: the essence of thunder, at least the basic part of it, is what causes noise to be in the clouds: quenching of fire. This is a powerful ‘two-in-one’ model: in Aristotle’s view, the two questions –‘why is it (as it is)?’ and ‘what is it?’– are answered in the same way at the same time. In the present example of thunder the cause that is the same as the essence is the efficient cause. The same applies to the other cases of processes presented in the Posterior Analytics: the Earth’s screening of the Sun’s light (the cause of lunar eclipse) and the solidification of sap at the leaf-nodes of broad-leafed plants (the cause of leaf-shedding).

In his MetaphysicsAristotle takes up both of the points I just highlighted about CEM. First, apart from cases of processes, he also extends this model to substance-kinds such as human or horse. Second, he insists that the essence is somehow the same as the cause. For the cases of processes such as thunder or eclipse the essence is the efficient cause. In substance cases, especially in living beings, it is the same as the final cause. Hence, being a human (the essence of the human kind) is the same as the relevant final cause, perhaps something like being for the sake of realising a certain sort of rational life. In other cases, such as basic chemical elements, the essence is presumably identifiable with their material constituents, together with their configuration or arrangement and perhaps also their relevant capacities for motion or change. But even in abstract cases, such as those of mathematical entities Aristotle may be able to identify the essence with an attenuated notion of material cause. For example, the essence of a triangle may be the same as the geometrical constituents of a triangle –points, lines, and angles– plus their configuration– on a plane and in a closed arrangement.

Let’s focus on the substance cases. Aristotle’s CEM, as it is developed in the Posterior Analytics, invokes an intimate link between explanatory demonstration and definition (in the strong, scientific or real-world sense discussed earlier). This link is undergirded by the metaphysical interdependence or sameness between cause (which is the real-world correlate of explanatory demonstration) and essence (the ‘real’ analogue of definition). The explanatory demonstration for thunder is roughly as follows:
Noise belongs to (in the sense of ‘is brought on by’) all quenching of fire.
Quenching of fire belongs to all clouds of a certain type.
Therefore, noise belongs to all clouds of a certain type.

Because of the close link between explanatory demonstration and definition we can read off from this sort of demonstration the scientific definition of thunder:
Thunder is defined as noise belonging to clouds of a certain type brought on by fire quenching.
For CEM to apply to substance cases we have to see whether we can offer a similar structure for an example such as the kind human. Indeed, Aristotle provides the basic ingredients to construct such a case:
Having a certain arrangement belongs to (in the sense of ‘is caused/explained by’) being human (the kind’s essence).
Being human belongs to bones, flesh, tissues, etc. of a certain sort.
Therefore, having a certain arrangement belongs to bones, flesh, tissues, etc. of a certain sort.

Clearly, this ‘explanatory’ demonstration is not terribly explanatory: for the cause or explanation, picked out by its middle term (the term that is common to both premisses), is being human, which is exactly what should be explained or/and defined. But Aristotle has identified the essence, being human, with the final cause. If we suppose that in the present case this is something like being for the sake of realising a rational life of a certain sort, the demonstration is immediately improved. Hence, the related definition would be:
Human kind is defined as a type of living being made of flesh, bones, tissues, etc. of a certain sort with a certain arrangement for the sake of realising a certain type of rational life.

Obviously, this definition, too, just as the related demonstration, contains several vague terms (‘certain type’;
‘certain sort’; etc.). But, as suggested earlier, such gaps are to be filled in by proper scientific inquiry: biology, physiology, psychology, etc. They are not to be spelt out on the basis of a priori conceptual analysis by itself. If this is correct, CEM can be applied to substance cases too.
There are several questions we could raise about CEM and its application to substances. I’ll discuss briefly just three. First, how does the CEM treatment fit with Aristotle’s hylomorphism, his idea that substances (inter alia) are matter—form compounds? To answer this question we have to see whether there are possible candidates to discharge the roles of matter, form, and compound in CEM. Looking again at the sample definition of human just given, we can indeed find such candidates. The definiendum, the human kind, is the compound (as is each particular human). It is also straightforward to identify the matter as the bones, flesh, tissues, etc. of a certain sort. But what about the form, which is the primary substance, what fixes the nature of the compound and its matter? There are competing candidates for this role. On the one hand, we have the arrangement or shape of the bodily constituents. On the other, we have the essence, being human, identified as the final cause, being for the sake of a certain type of rational life. Both look pretty form-like. It would constitute a case of formal over-determination if there were two forms determining the nature of the compound. There are several possible ways to overcome this difficulty. Let me present dogmatically my view. I think that the arrangement or shape of the bones, flesh, etc. is what or how matter actually is. This intimate link of the ‘shapy’ feature with matter implies that it is not the bedrock formal item. Rather, I take the essence which is identified with the final cause (being for the sake of a rational life) as the fundamental form which fixes the identity of the matter, its shape, but also grounds their intimate link. This sort of arrangement (say, the presence of a pair of hands, arms, feet, and legs) belongs to the bodily constituents (flesh and bones) for the sake of (or because of) realising a certain sort of rational life (for example, our hands enable us to wield tools, an important capacity stemming from our rationality).

Second, the traditional conception of Aristotelian definitions suggests that they are framed in terms of a ‘genus plus differentia’: a species such as human is defined as an animal (the genus) which is biped and rational (the differences). How, if at all, does this model fit with CEM? This is another difficult question. Some interpreters answer it in a ‘developmentalist’ fashion. While Aristotle subscribed to the genus-differentia model in his earlier, logical works, he abandoned it in favour of CEM in his later, scientific and metaphysical works. This reply is not satisfactory. Another idea might be to think that the two models co-exist and are in tension but Aristotle never figured out how to reconcile them or which of the two to give up. Again this is not ideal. In my view, the genus-differentia model is not only consistent with (and so not in tension with) but also fully subordinated to CEM. For I would argue that genus-differentia accounts of substance kinds play the role of explananda, which are to be explained by the fundamental essence or cause of CEM. For example, suppose that the relevant shape or arrangement is cognate with the differentia being biped, while the matter thus shaped or arranged is a genus-like item such as animal or animal body (of a certain sort). CEM could accommodate this genus-differentia account within the first segment of the sort definition it provides. The second segment, then, would encapsulate the basic essence or cause, which explains why a certain differentia belongs to a genus in the way it does. Our sample definition would be recast as follows:
Human kind is defined as being biped belonging to animal for the sake of realising a certain sort of rational life,
or something along these lines. While schematic, this idea would be a neat way to integrate the two different models. I would like to develop it further in future work.

Third, the crucial idea behind CEM is that essence and cause are somehow the same. This is what underwrites the close link between explanatory demonstration and definition and what gets the whole model off the ground. But what is the precise ‘how?’ of sameness in this model? There are several options. First, one may strictly identify essence with cause, without favouring one or the other as basic. In this approach, perhaps essence and cause are different ways of looking at, or different roles served by, what is explanatorily and metaphysically basic. Second, one may follow the route of reduction: either the notion of essence is reduced to that of cause, or the other way around. Third, one may think that the one notion is neither identical nor reducible to the other. Rather, they are indissolubly interdependent: one cannot characterise an essence without recourse to the specific cause it is. Nor can one specify a cause without revealing its identity-fixing operation. This Aristotelian notion of essence-cum-cause would satisfy the ‘two-in-one’ character of CEM: it would answer at the same time both the ‘what is it?’ and the ‘why is it (as it is)?’ questions. While this last option is attractive, it is unclear whether Aristotle explicitly distinguishes such varieties of sameness or, even if he does, what he would say specifically about the relation between essence and cause.

3:AM:As a take home then about Aristotle’smetaphysics, can you summarise how you think we should understand priority in metaphysics?

MP:To answer this question, we should, in true Aristotelian fashion, be absolutely clear about the different parameters that are implicit in it. In understanding priority in Aristotle’s metaphysics we should first ask about the respect in which we are viewing priority: is it priority in time, in account, in definition, in knowledge, or in being, substance, and nature? I argue that the central notion, in the sense of what plays the role of a criterion for what counts as fundamentally real –Aristotle’s primary substance– or even in the sense of what being fundamentally real (partly) consists in, is ontological priority (in respect of being, substance, or nature). A more practical parameter, which is helpful in coming to grips with priority in metaphysics, is to examine what the relevant relata are and how they may affect our conception of priority. This parameter also has an important exegetical corollary: we have to be sensitive to Aristotle’s examples of prior and posterior items, and to ascertain whether our construal of priority can accommodate such examples. I think that many interpreters were (some perhaps still are) in some sort of dogmatic slumber, to use the Kantian metaphor, in that they insisted on the modal-existential construal despite the fact that it cannot make good sense of Aristotle’s examples. I approach ontological priority with a view to enabling Aristotle’s primary substance (the essence or form) to be ontologically prior to matter and compounds. Using these and other similar considerations I would summarise Aristotelian ontological priority as the asymmetric relation of a basic item’s making some other, derivative item what it essentially is. I would also emphasise that to support the asymmetry (the ‘not conversely’) of this priority relation –to avoid the charge that we simply stipulate what constitutes the essence of what– we should back up the relation of making something what it is using causal-explanatory relations anchored in the real world (such as those I mentioned in my discussion of CEM in reply to the previous question): efficient causation for processes, final causation for substances, material causation for basic stuffs, and some abstract analogue of material causation for mathematical or other abstract entities.

3:AM:And can you give examples of how this perspective might impact upon contemporary metaphysics – for example, would ideas about causality change from this account you give?

MP:I touched on this issue in my response to your earlier question. It might be useful to outline three main areas in which the Aristotelian perspective on priority (and other central metaphysical concepts) could prove helpful in contemporary metaphysics.

First, drawing on Aristotelian ideas we could escape the tyranny of Humean, narrowly construed efficient causation in our debates about causation. Making conceptual space for other sorts of causation, such as material, formal, and final causation, and emphasising the interdependence between causation and explanation may offer a way out of intellectual impasses in those debates.

Second, I think that the idea I introduced in reply to question about the sameness or interdependence between essence and cause– can help in our attempts to offer a plausible account of essentialism. Stephen Yablo, among others, has written on the relation between essence and cause but with a slightly different focus (on the philosophy of mind). Neo-Aristotelian approaches to essentialism, such as Kit Fine’s view, would benefit from adopting this idea of sameness or interdependence: instead of relying on an intuitive conception of what constitutes an object’s essence (by contrast to what follows from this constitutive essence and resides in what Fine calls ‘consequential’ essence), an essence-cum-cause account of essentialism is more rigorous and can underpin the priority of essence over merely modal necessity.

And this brings me to the third point: the Aristotelian picture I have adumbrated can provide a better account of modality. The intimate link between essence, cause, and explanation can shed light on the source of and ground for our necessity and possibility claims more satisfactorily than possible world views of modality. Several modern metaphysicians work on potentiality and powers –another central Aristotelian concept– and this may be the ‘middle term’, as it were, which will connect essence and causation, on the one hand, and modality, on the other, in a plausible and robust way. Perhaps, an essence that is identified as a cause just is or supports an integrated group of powers which operate as grounds for, or truth-makers of, modal claims. It will be fascinating to see the different directions into which metaphysical thought will be driven in the near future as a result of discussions in these three areas (and other areas as well!).

3:AM:And finally, are there five books you could recommend that will take us further into your philosophical world?

MP:Since there is no requirement to restrict my recommendations to just Ancient authors or just contemporary works, I’ll compile a ‘mixed’ list. The first entry is double, so I’ll in fact give six recommendations (if I may).

Aristotle’s Posterior Analyticsand his Metaphysicsare a good way to delve deeper into the philosophical world I inhabit. Posterior Analytics presents his theory of scientific demonstration and explanation –a first attempt at theorising about axiomatised bodies of knowledge– but also discusses scientific inquiry (see my response to question 11). It also invokes basic tenets of Aristotle’s theory of syllogistic deduction, set out in the Prior Analytics, so in a way it could be seen as a seminal ‘logic of science’. But this work is not just a philosophy of science in the narrow sense. It discusses central issues in epistemology, metaphysics, explanation, essentialism, necessity, predication, meaning, and definition. His Metaphysics, on the other hand, is an even more wide-ranging work. It raises all or most of the questions we still discuss nowadays in metaphysics (notably, without ever using the title ‘metaphysics’; Aristotle uses ‘wisdom’, ‘first philosophy’, and sometimes ‘theology’): the nature of metaphysics itself; its central puzzles; the Principles of Non-Contradiction and of the Excluded Middle; a list of important (and some less important) metaphysical concepts (principle; element; nature; necessity; being; substance; priority; etc.); accidental and contingent beings; truth; substance and essence; form, matter, and compound; potentiality and actuality; unity; theology; and the nature of mathematical objects. There are many other topics, questions, and answers which are discussed in connection with the central areas I just listed. Both the Posterior Analytics and the Metaphysicsare difficult but extremely rewarding works.

The second work is Plato’s Theaetetus. This dialogue is ostensibly about the nature of knowledge and, in this respect, it is an exemplary work in epistemology, perhaps the insuperable masterpiece. But it deals with so many other related questions, offers such a plethora of arguments and counter-arguments, and sets out so many philosophical positions and attempts to refute them that it is not just a treatise in epistemology narrowly construed. It discusses perception, relativism, language, thought, belief, falsity, and ‘logos’ –what could be translated as explanation, justification, differentiating mark (‘differentia’), or definition (among many other possible renderings). It offers three definitions of knowledge and rejects all three of them. The third definition, in terms of true belief plus logos, can be seen as Plato’s version of a ‘justified true belief’ account of knowledge (JTB). The final refutation offered against that definition constitutes a powerful argument, which (I think) cannot be overcome by any JTB account, not even by modern views of this sort.

The third book is David Charles’s Aristotle on Meaning and Essence. It is among the works at the centre of my philosophical world for several reasons. David Charles was the supervisor of my doctorate. But we still work together, discussing each other’s papers, reading and criticising others’ works, co-authoring papers and books. Another reason why this book is important for me is that it is a paradigm of the approach to Ancient Philosophy I referred to earlier (in reply to your question 3) as ‘philosophical scholarship’ (this is the characterisation he himself gives to this approach in another work of his, Aristotle’s Philosophy of Action). Not only does he discuss some of the most difficult and controversial texts in Aristotle’s works in an admirably lucid and rigorous way. He also links Aristotle’s views and arguments to modern philosophical questions and shows how Aristotelian ideas can give plausible solutions to problems in epistemology, metaphysics, and the philosophy of language.

As a fourth recommendation I’ll include Timothy Williamson’sKnowledge and Its Limits. This book refreshed my interest in epistemology. It offers a ground-breaking account in which knowledge is to be understood as the basic and most general factive (i.e. truth-attaining) mental state. While traditional epistemologies define knowledge using some highly contrived and ad hoc version of a JTB account, Williamsonputs ‘knowledge first’: knowledge defines other mental states, such as belief, assertion, remembering, etc., while it itself is not defined in terms of any conceptually more basic mental state: for there is no mental state that is more basic than it. The book is close to my heart because it treats its subject-matter with the sort of precision, clarity, and rigour that is characteristic of the most excellent contributions of analytical philosophy. But it also argues for an epistemological view which, I think, is congenial to Plato’s and Aristotle’s views of knowledge. I have written a paper on Aristotle’s distinction between knowledge and true belief which has benefitted greatly from Williamson’swork. I also plan to write a paper on why Plato would never define knowledge in terms of (true) belief, another point which is at the heart of ‘knowledge first’ epistemology. Moreover, Williamson’s discussion of primeness has led me to believe that there is an interesting analogy between the primeness of knowledge and the unity of form in Aristotle’s hylomorphism, an idea I am currently developing into a paper.

My fifth and last recommendation would be Stathis Psillos’s Scientific Realism: How Science Tracks Truth. While there is a great number of modern philosophical books which have influenced my thought and are part of my intellectual world, this is a work that combines seamlessly all of my interests in theoretical philosophy: metaphysical questions of realism; explanation and causation; meaning and reference; scientific progress, theory change, and theory choice; applications of logic to the philosophy of science. It is structured clearly and argued meticulously. While it is effectively a work in the philosophy of science, it constitutes a model of theoretical analytical philosophy. Another, more autobiographical reason for recommending it is that Stathis Psilloswas among my teachers during my MSt studies in Greece, someone whom I looked and still look up to, and one of the philosophers who helped me become the sort of thinker I now am.

Richard Marshallis still biding his time.

Buy his new book hereor his first book hereto keep him biding!