1Metaphysical realism is the view that most of the objects that populate the world exist independently of our thought and have their natures independently of how, if at all, we conceive of them. Metaphysical realism is committed, in my opinion, to a robust form of essentialism, that is, to the doctrine that there are mind-independent facts about the identities of most objects. ‘Identity’ in this sense means individual essence, which John Locke aptly characterized as ‘ the very being of any thing, whereby it is, what it is’. Many modern forms of anti-realism have their basis in a form of conceptualism, according to which all truths about essence knowable by us are ultimately grounded in our concepts — that is, in our ways of thinking about things — rather than in things ‘in themselves'. This view has its historical roots in Immanuel Kant’s critical philosophy, so that contemporary conceptualist anti-realism may, without undue distortion, be described as ‘neo-Kantian’ in spirit. This is despite the fact that one important way in which its adherents differ from the historical Kant is in their emphasis upon language as the medium of thought, as a result of the so-called ‘linguistic turn’ in philosophy that occurred in the early-to-mid twentieth century.

2My aim in the present paper is to show that and why conceptualist anti-realism is an incoherent doctrine and why and how we can and must support metaphysical realism and robust essentialism, while still properly acknowledging the cognitive role of concepts in mediating our grasp of the nature of mind-independent reality. I shall begin with a sketch of the version of essentialism that I favour — a version that I call serious essentialism — and in the course of doing so I shall identify its three key principles. Then I shall try to explain why I think that conceptual-ism can provide no adequate substitute for this form of essentialism and inevitably collapses into an incoherent variety of global anti-realism.

3It is vital for my purposes in this paper that the doctrine of essentialism be suitably understood. I say this because many contemporary possible-worlds theorists readily describe themselves as essentialists and propose and defend what they call essentialist claims, formulated in terms of the language of possible worlds. They will say, for instance, that an essential property of an object is one that the object possesses in every possible world in which it exists. And they will typically claim that some, but not all, of an object’s actual properties are essential to it in this sense. But a doctrine of this sort is not serious essentialism in my sense, because it attempts to characterize essence in terms of antecedently assumed notions of possibility and necessity and thus — in my view — puts the cart before the horse. It is at best ersatz essentialism. So what is serious essentialism? To pursue this query, one might seek to ask what essences are. However, this question is already potentially misleading, for it invites the reply that essences are entities of some special sort. And, as we shall see, I want to deny that essences are entities. According to serious essentialism, as I understand it, all entities have essences, but their essences are certainly not further entities related to them in some special way.

1 The historical source of this view lies, of course, with Aristotle, whose phrase το τι ην ειναι (‘ (...)

The historical source of this view lies, of course, with Aristotle, whose phrase το τι ην ειναι (‘ (...) 2 I do not attempt to offer here a semantic analysis of expressions such as ‘what X is’, ‘what it is (...)

I do not attempt to offer here a semantic analysis of expressions such as ‘what X is’, ‘what it is (...) 3 For my own account of what ontological categories we should recognize and which we should regard a (...) 4So, what do we or, rather, what should we mean by the ‘essence’ of a thing — where by ‘thing’, in this context, I just mean any sort of entity whatever? We can, I suggest, do no better than to recall John Locke’s perceptive words on the subject, which go right to its heart. Essence, Locke said, in the ‘proper original signification’ of the word, is ‘the very being of any thing, whereby it is, what it is’ [Locke 1975, III, III, 15]. In short, the essence of something, X, is what Xis, or what it is to be X. In another locution, X’s essence is the very identity of X — a locution that I am happy to adopt, provided that it is clearly understood that to speak of something’s ‘identity’ in this sense is quite different from speaking of the identity relation in which it necessarily stands to itself and to no other thing. However, in order to avoid potential confusion about the meaning of locutions such as these, I think that it is important to draw, from the very start, a distinction between general and individual essence . The key point to be emphasized in this connection is that any individual thing, X, must be a thing of some general kind — because, at the very least, it must belong to some ontological category. Remember that by ‘thing’ here I just mean ‘entity’. So, for example, X might be a material object, or a person, or a property, or a set, or a number, or a proposition, or whatnot — the list goes on, in a manner that depends on what one takes to be a full enumeration of the ontological categories to be included in it . This point being accepted, if X is something of kind K, then we may say that X’s general essence is what it is to be a K, while X ’s individual essence is what it is to be the individual of kind K that X is, as opposed to any other individual of that kind.

5Before I proceed, however, an important complication must be dealt with. It should be evident that we cannot simply assume that there is only ever a single appropriate answer to the question ‘What kind of thing is X?’. For instance, if ‘a cat’ is an appropriate answer to this question, then so will be the answers ‘an animal’ and ‘a living organism’. So too, of course, might be the answer ‘a Siamese cat’. It is important to recognize, however, that some, but not all, of these answers plausibly announce the fact that X belongs to a certain ontological category. In my own view, 'X is a living organism’, does announce such a fact, but ‘X is a cat’ does not. I take it that the substantive noun ‘cat’ denotes a certain natural kind and consider that such kinds are a species of universal. Thus, as I see it, natural kinds, such as the kind cat, are themselves things belonging to a certain ontological category — the category of universals — but such a kind is not itself an ontological category, because ontological categories are not things at all, to be included in a complete inventory of what there is (see [Lowe 1998, ch. 8] and [Lowe 2006, ch. 2]). One upshot of all this is that I want to maintain that a certain sort of ambiguity may attach to questions concerning a thing’s general essence, as I shall now try to explain.

4 I want to maintain that X’s fundamental general essence determines what is absolutely metaphysical (...)

I want to maintain that X’s fundamental general essence determines what is absolutely metaphysical (...) 5 I take it here, at least for the sake of argument, that there are ‘higher’ natural kinds to which (...)

I take it here, at least for the sake of argument, that there are ‘higher’ natural kinds to which (...) 6 One consequence of this simplification is that I shall often continue to speak of ‘the kind to whi (...) 6An implication of what I have said so far is that if ‘a cat’ is an appropriate answer to the question ‘What kind of thing is X?’, then we may say that X’s general essence is what it is to be a cat. But, while I don’t want to retreat from this claim, I do want to qualify it. I should like to say that if X is a cat, then X’s fundamental general essence is what it is to be a living organism, because that — in my view — is the most narrow (or ‘lowest’) ontological category to which X may be assigned. The reason for this is that it is part of the individual essence of the natural kind cat — of which X is ex hypothesi a member — that it is a kind of living organisms. Now, there are, I believe, certain essential truths concerning X which do not issue from its fundamental general essence but only from the fact that it belongs to this particular natural kind. These are essential truths concerning X which are determined solely by the individual essence of that natural kind . Accordingly, I want to say that what it is to be a cat, while it is not X’s fundamental general essence, is nonetheless what we might appropriately call X’s specific general essence, on the grounds that the kind cat is the most specific (or ‘lowest’) natural kind to which X may be assigned . However, I readily acknowledge that the distinction that I am now trying to draw between ‘fundamental’ and ‘specific’ general essence in the case of individual members of natural kinds is a controversial one that needs much fuller justification than I am able to give it here. Hence, in what follows, I shall try as far as possible to prescind from this distinction, hoping that the simplification involved in doing so will cause no damage to the overall thrust of my arguments .

7 Note that I ask only how we can talk or think comprehendingly about a thing if we do not know what (...)

Note that I ask only how we can talk or think comprehendingly about a thing if we do not know what (...) 8 Perhaps, indeed, all I need to know about cats is that they are animals or living organisms and pe (...)

Perhaps, indeed, all I need to know about cats is that they are animals or living organisms and pe (...) 9 Of course, it is fashionable at present to suppose that our talk and thought have, in general, the (...) 7I have just urged that all individual things — all entities — have both general and individual essences, a thing’s general essence being what it is to be a thing ofits kind and its individual essence being what it is to be the individual ofthat kind that it is, as opposed to any other individual of that kind. But why suppose that things must have ‘essences’ in this sense and that we can, at least in some cases, know those essences? First of all, because otherwise it makes no sense — or so I believe — to say that we can talk or think comprehendingly about things at all. For if we do not at least know what a thing is, how can we talk or think comprehendingly about it? How, for instance, can I talk or think comprehendingly about Tom, a particular cat, if I simply don’t know what cats are and which cat, in particular, Tom is? Of course, I’m not saying that I must know everything about cats or about Tom in order to be able to talk or think comprehendingly about that particular animal . But I must surely know enough to distinguish the kind of thing that Tom is from other kinds of thing, and enough to distinguish Tom in particular from other individual things of Tom’s kind. Otherwise, it seems that my talk and thought cannot really fasten upon Tom, as opposed to something else . However, denying the reality of essences doesn’t only create an epistemological problem: it also creates an ontological problem. Unless Tom has an ‘identity’ — whether or not anyone is acquainted with it — there is nothing to make Tom the particular thing that he is, as opposed to any other thing. Anti-essentialism commits us to anti-realism, and indeed to an anti-realism so global that it is surely incoherent. It will not do, for instance, to try to restrict one’s anti-essentialism to ‘the external world’, somehow privileging us and our language and thought. How could it be that there is a fact of the matter as to our identities, and the identities of our words and thoughts, but not as to the identities of the mind-independent entities that we try to capture in language and thought? On the other hand, how could there not be any fact of the matter as to our identities and the identities of our words and thoughts? Everything is, in Joseph Butler’s memorable phrase, what it is and not another thing. That has sounded to many philosophers like a mere truism without significant content, as though it were just an affirmation of the reflexivity of the identity relation. But, in fact, Butler’s dictum does not merely concern the identity relation but also identity in the sense of essence. It implies that there is a fact of the matter as to what any particular thing is — that is, as to its ‘very being’, in Locke’s phrase. Its very being — its identity — is what makes it the thing that it is and thereby distinct from any other thing.

10 There are, broadly speaking, two different views of what a set is: one which takes a set simply to (...) 8Essences are apt to seem very elusive and mysterious, especially if talked about in a highly generalized fashion, as I have been doing so far. Really, I suggest, they are quite familiar to us. Above all, we need to appreciate that in very many cases a thing’s essence involves other things, to which it stands in relations of essential dependence. Consider the following thing, for instance: the set of planets whose orbits lie within that of Jupiter. What kind of thing is that? Well, of course, it is a set, and as such an abstract entity that depends essentially for its existence and identity on the things that are its members — namely, Mercury, Venus, Earth, and Mars. Part of what it is to be a set is to be something that depends in these ways upon certain other things — the things that are its members. Someone who did not grasp that fact would not understand what a set is. Furthermore, someone who did not know which things are this set’s members, or at least what determined which things are its members, would not know which particular set this set is. So, someone who knew that its members are the planets just mentioned would know which set it is, as would someone who knew what it is to be a planet whose orbit lies within that of Jupiter . This is a simple example, but it serves to illustrate a general point. In many cases, we know what a thing is — both what kind of thing it is and which particular thing of that kind it is — only by knowing that it is related in certain ways to other things. In such cases, the thing in question depends essentially on these other things for its existence or its identity. To say that X depends essentially on Y for its existence and identity is just to say that it is part of the essence of X that X exists only if Y exists and part of the essence of X that X stands in some unique relation to Y (see [Lowe 1998, ch. 6], or [Lowe 2005a]). Knowing a thing’s essence, in many cases, is accordingly simply a matter of understanding the relations of essential dependence in which it stands to other things whose essences we in turn know.

11 Thus, at one point Locke remarks: ‘[W]e come to have the Ideas of particular sorts of Substances, (...) 9I said earlier that it is wrong to think of essences as themselves being entities of any kind to which the things having them stand in some special kind of relation. Locke himself unfortunately made this mistake, holding as he did that the ‘real essence’ of a material substance just is its ‘particular internal constitution’ — or, as we would now describe it, its atomic or molecular structure . This is a mistake that has been perpetuated in the modern doctrine, made popular by the work of Saul Kripke and Hilary Putnam, that the essence of water consists in its molecular make-up, H 2 O, and that the essence of a living organism consists in its DNA — the suggestion being that we discover these ‘essences’ simply by careful scientific investigation of the things in question (see, especially, [Kripke 1980] and [Putnam 1975]). Now, as we saw earlier, it may well be part of the essence of a thing that it stands in a certain relation to some other thing, or kind of things. But the essence itself — the very being of a thing, whereby it is, what it is — is not and could not be some further entity. So, for instance, it might perhaps be acceptable to say that it is part of the essence of water that it is composed of H 2 O molecules (an issue that I shall return to shortly). But the essence of water could not simply be H 2 O — molecules of that very kind — nor yet the property of being composed of H 2 O molecules. For one thing, if the essence of an entity were just some further entity, then it in turn would have to have an essence of its own and we would be faced with an infinite regress that, at worst, would be vicious and, at best, would appear to make all knowledge of essence impossible for finite minds like ours. To know something’s essence is not to be acquainted with some further thing of a special kind, but simply to understand what exactly that thing is. This, indeed, is why knowledge of essence is possible, for it is a product simply of understanding — not of empirical observation, much less of some mysterious kind of quasi-perceptual acquaintance with esoteric entities of any sort. And, on pain of incoherence, we cannot deny that we understand what at least some things are, and thereby know their essences.

10Here it may be objected that it is inconsistent of me to deny that essences are entities and yet go on, as I apparently do, to refer to and even quantify over essences. Someone who voices this objection probably has in mind W. V. Quine’s notorious criterion of ontological commitment, encapsulated in his slogan ‘to be is to be the value of a variable’ [see, for example, Quine 1969]. I reply, in the first place, that I could probably say all that I want to about my version of essentialism while avoiding all locutions involving the appearance of reference to and quantification over essences, by paraphrasing them in terms of locutions involving only sentential operators of the form ‘it is part of the essence of X that’ — where ‘the essence of X’ is not taken to make an independent contribution to the meaning of the operator, which might be represented symbolically by, say, ‘E X ’ in a sentential formula of the form ‘E X (p)’. The latter is a kind of locution that I certainly do want to use and find very useful. However, I think that effort spent on working out such paraphrases in all cases would be effort wasted. If a paraphrase means the same as what it is supposed to paraphrase — as it had better do, if it is to be any good — then it carries the same ‘ontological commitments’ as whatever it is supposed to paraphrase, so that constructing paraphrases cannot be a way of relieving ourselves of ontological commitments. We cannot discover those commitments simply by examining the syntax and semantics of our language, for syntax and semantics are very uncertain guides to ontology. In other words, I see no reason to place any confidence in Quine’s famous criterion.

12 Notoriously, Descartes is supposed to have claimed, in the Second Meditation, to know that he exis (...) 11Another crucial point about essence is this: in general, essence precedes existence. And by this I mean that the former precedes the latter both ontologically and epistemically. That is to say, on the one hand, I mean that it is a precondition of something’s existing that its essence — along with the essences of other existing things — does not preclude its existence. And, on the other hand — and this is what I want to concentrate on now — I mean that we can in general know the essence of something X antecedently to knowing whether or not X exists. Otherwise, it seems to me, we could never find out that something exists. For how could we find out that something, X, exists before knowing what X is — before knowing, that is, what it is whose existence we have supposedly discovered? Consequently, we know the essences of many things which, as it turns out, do not exist. For we know what these things would be, if they existed, and we retain this knowledge when we discover that, in fact, they do not exist. Conceivably, there are exceptions. Perhaps it really is true in the case of God, for instance, that essence does not precede existence. But this could not quite generally be the case. However, saying this is perfectly consistent with acknowledging that, sometimes, we may only come to know the essence of something after we have discovered the existence of certain other kinds of things. This is what goes on in many fields of theoretical science. Scientists trying to discover the transuranic elements knew before they found them what it was that they were trying to find, but only because they knew that what they were trying to find were elements whose atomic nuclei were composed of protons and neutrons in certain hitherto undiscovered combinations. They could hardly have known what they were trying to find, however, prior to the discovery of the existence of protons and neutrons — for only after these sub-atomic particles were discovered and investigated did the structure of atomic nuclei become sufficiently well-understood for scientists to be able to anticipate which combinations of nucleons would give rise to reasonably stable nuclei.

13 The extent to which the Kripke-Putnam doctrine has become a commonplace of contemporary analytic p (...) 12Here it may be objected that Kripke and Putnam have taught us that the essences of many familiar natural kinds — such as the kind cat and the kind water — have been revealed to us only a posteriori and consequently that in cases such as these, at least, it cannot be true to say that ‘essence precedes existence’, whatever may be said in the case of the transuranic elements . The presupposition here, of course, is that Kripke and Putnam are correct in identifying the essence of water, for example, with its molecular make-up, H 2 O. Now, I have already explained why I think that such identifications are mistaken, to the extent that they can be supposed to involve the illicit reification of essences. But it may still be urged against me that even if, more cautiously, we say only that it is part of the essence of water that it is composed of H 2 O molecules, it still follows that the essence of water has only been revealed to us — or, at least, has only been fully revealed to us — a posteriori.

14 See [Kripke 1971]. I express doubts about the cogency of this proof in [Lowe 2005b]. However, for (...)

See [Kripke 1971]. I express doubts about the cogency of this proof in [Lowe 2005b]. However, for (...) 15 Here I note that it might be thought that ‘Water is the stuff composed of H 2 O molecules’ follows u (...) 13In point of fact, however, the Kripke-Putnam doctrine is even more obscure and questionable than I have so far represented it as being. Very often, it is characterized in terms of the supposed modal and epis-temic status of identity-statements involving natural kind terms, such as ‘Water is H 2 O, which are said to express truths that are at once necessary and a posteriori. In such a statement, however, the term ‘H 2 O’ is plainly not functioning in exactly the same way as it does in the expression ‘H 2 O molecule’. The latter expression, it seems clear, means ‘molecule composed of two hydrogen ions and one oxygen ion’. But in ‘Water is H 2 O’, understood as an identity-statement concerning kinds, we must either take ‘H 2 O’ to be elliptical for the definite description ‘the stuff composed of H 2 O molecules’ or else simply as being a proper name of a kind of stuff, in which case we cannot read into it any significant semantic structure. On the latter interpretation, ‘Water is H 2 O’ is exactly analogous to ‘Hesperus is Phosphorus’ and its necessary truth reveals nothing of substance to us concerning the composition of water. If we are inclined to think otherwise, this is because we slide illicitly from construing ‘H 2 O’ as a proper name to construing it as elliptical for the definite description ‘the stuff composed of H 2 O molecules’. Now, when ‘Water is H 2 O ’ is understood on the model of ‘Hesperus is Phosphorus’, its necessary a posteriori truth may in principle be established in a like manner — namely, by appeal to the familiar logical proof of the necessity of identity , together with the a posteriori discovery of the co-reference of the proper names involved — but not so when it is construed as meaning ‘Water is the stuff composed of H 2 O molecules’, for the latter involves a definite description and the logical proof in question notoriously fails to apply where identity-statements involving definite descriptions are concerned. Thus far, then, we have been given no reason to suppose that ‘Water is H 2 O’ expresses an a posteriori necessary truth that reveals to us something concerning the essence of water. The appearance that we have been given such a reason is the result of mere sleight of hand .

16 Here it may be asked: did astronomers know which planet Hesperus is — that is, know its individual (...) 14There is, in any case, another important consideration that we should bear in mind when reflecting on the frequently-invoked analogy between ‘Water is H 2 O’ and ‘Hesperus is Phosphorus’. It is all very well to point out that the discovery that Hesperus is Phosphorus was an empirical one. But it was not purely empirical, for the following reason. The identity was established because astronomers discovered that Hesperus and Phosphorus coincide in their orbits: wherever Hesperus is located at any given time, there too is Phosphorus located. However, spatiotemporal coincidence only implies identity for things of appropriate kinds. It is only because Hesperus and Phosphorus are taken to be planets and thereby material objects ofthe same kind that their spatiotemporal coincidence can be taken to imply their identity. But the principle that distinct material objects of the same kind cannot coincide spatiotempo-rally is not an empirical one: it is an a priori one implied by what it is to be a material object of any kind — in other words, it is a truth grounded in essence. It is only because we know that it is part of the essence of a planet not to coincide spatiotemporally with another planet, that we can infer the identity of Hesperus with Phosphorus from the fact that they coincide in their orbits. Thus, one must already know what a planet is — know its essence — in order to be able to establish by a posteriori means that one planet is identical with another . By the same token, then, one must already know what a kind of stuff is — know its essence — in order to be able to establish by a posteriori means that one kind of stuff is identical with another. It can hardly be the case, then, that we can discover the essence of a kind of stuff simply by establishing a posteriori the truth of an identity-statement concerning kinds of stuff — any more than we can be supposed to have discovered the essence of a particular planet by establishing a posteriori the truth of an identity-statement concerning that planet. So, even granting that ‘Water is H 2 O’ is a true identity-statement that is both necessarily true and known a posteriori, it does not at all follow that it can be taken to reveal to us the essence of the kind of stuff that we call ‘water’.

17 For extended discussion of the need to distinguish between these two species of possibility, see [ (...) 15Be all this as it may, however, we still have to address the question of whether, in fact, we ought to say that it is part of the essence of water that it is composed of H 2 O molecules. So far, we have at best seen only that the Kripke-Putnam semantics for natural kind terms have given us no reason to suppose that we ought to. I am inclined to answer as follows. If we are using the term ‘water’ to talk about a certain chemical compound whose nature is understood by theoretical chemists, then indeed we should say that it is part of the essence of this compound that it consists of H 2 O molecules. But, at the same time, it should be acknowledged that the existence of this compound is a relatively recent discovery, which could not have been made before the nature of hydrogen and oxygen atoms and their ability to form molecules were understood. Consequently, when we use the term ‘water’ in everyday conversation and when our forebears used it before the advent of modern chemistry, we are and they were not using it to talk about a chemical compound whose nature is now understood by theoretical chemists. We are and they were using it to talk about a certain kind ofliquid, distinguishable from other kinds of liquid by certain fairly easily detectable macroscopic features, such as its transparency, colourlessness, and tastelessness. We are right, I assume, in thinking that a liquid of this kind actually exists, but not that it is part of its essence that it is composed of H 2 O molecules. At the same time, however, we should certainly acknowledge that empirical scientific inquiry reveals that, indeed, the chemical compound H 2 O is very largely what bodies of this liquid are made up of. In fact, the natural laws governing this and other chemical compounds make it overwhelmingly unlikely that this kind of liquid could have a different chemical composition in different parts of our universe. But the ‘could’ here is expressive of mere physical or natural possibility, not metaphysical possibility . Only an illicit conflation of these two species of possibility could reinstate the claim that water is essentially composed of H 2 O molecules.

16But, it may be asked, what about our supposed ‘intuitions’ in so-called ‘Twin-Earth’ cases — for example, the supposed intuition that if, on a distant planet, a watery stuff was discovered that was not composed of H 2 O molecules, then it would not be water? In answer to this question, I would remark only that these supposed intuitions need to be interpreted in the light of the fact, just mentioned, that the natural laws governing chemical compounds in our universe almost certainly render such scenarios physically impossible. The supposedly ‘watery’ stuff on Twin Earth would be like fool’s gold (copper pyrites): it would at best be casually mistakable for water and that is why it would not be water. The chemical explanation for this would be that it is not composed of H 2 O molecules. But we cannot turn this perfectly legitimate chemical explanation into a logico-cum-metaphysical argument that genuine water is of metaphysical necessity composed of H 2 O molecules — unless, once again, we conflate physical with metaphysical necessity.

18 Note that analogously, then, it could be conceded that H 2 O molecules necessarily compose water wit (...) 17So far, I have urged that the following two principles must be endorsed by the serious essentialist: that essences are not entities and that, in general, essence precedes existence. But by far the most important principle to recognize concerning essences, for the purposes of the present paper, is that essences are the ground of all metaphysical necessity and possibility (compare [Fine 1994]). One reason, thus, why it can be the case that X is necessarily F is that it is part of the essence of X that X is F. For example, any material object is necessarily spatially extended because it is part of the essence of a material object that it is spatially extended — in other words, part of what it is to be a material object is to be something that is spatially extended. But this is not the only possible reason why something may be necessarily F. X may be necessarily F on account of the essence of something else to which X is suitably related. For example, Socrates is necessarily the subject of the following event — the death ofSocrates — because it is part of the essence of that event that Socrates is its subject, even though it is not part of Socrates’s essence that he is the subject of that event. It is not on account of what Socrates is that he is necessarily the subject of that event but, rather, on account of what that event is . This is not to say that Socrates could not have died a different death, only that no one but Socrates could have died the death that he in fact died. And what goes for necessity goes likewise, mutatis mutandis, for possibility. I venture to affirm that all facts about what is necessary or possible, in the metaphysical sense, are grounded in facts concerning the essences of things — not only of existing things, but also of non-existing things. But, I repeat, facts concerning the essences of things are not facts concerning entities of a special kind, they are just facts concerning what things are — their very beings or identities. And these are facts that we can therefore grasp simply in virtue of understanding what things are, which we must in at least some cases be able to do, on pain of being incapable of thought altogether. Consequently, all knowledge of metaphysical necessity and possibility is ultimately a product of the understanding, not of any sort of quasi-perceptual acquaintance, much less of ordinary empirical observation.

18How, for example, do we know that two distinct things of suitably different kinds, such as a bronze statue and the lump of bronze composing it at any given time, can — unlike two planets — exist in the same place at the same time? Certainly not by looking very hard at what there is in that place at that time. Just by looking, we shall not see that two distinct things occupy that place. We know this, rather, because we know what a bronze statue is and what a lump of bronze is. We thereby know that these are different things and that a thing of the first sort must, at any given time, be composed by a thing of the second sort, since it is part of the essence of a bronze statue to be composed of bronze. We know that they are different things because, in knowing what they are, we know their identity conditions, and thereby know that one of them can persist through changes through which the other cannot persist — that, for instance, a lump of bronze can persist through a radical change in its shape whereas a bronze statue cannot. These facts about their identity conditions are not matters that we can discover purely empirically, by examining bronze statues and lumps of bronze very closely, as we might in order to discover whether, say, they conduct electricity or dissolve in sulphuric acid (see further [Lowe 2003] and [Lowe 2002], the latter being a reply to [Olson 2001] ). Rather, they are facts about them that we must grasp antecedently to being able to embark upon any such empirical inquiry concerning them, for we can only inquire empirically into something’s properties if we already know what it is that we are examining..

19 Who, it might be asked, is really a conceptualist in the sense that I am about to articulate? That (...) 19At this point I need to counter a rival view of essence that is attractive to many philosophers but is, I think, ultimately incoherent. I call this view conceptualism. It is the view that what I have been calling facts about essences are really, in the end, just facts about certain of our concepts — for example, our concept of a bronze statue and our concept of a lump of bronze. This would reduce all modal truths to conceptual truths or, if the old-fashioned term is preferred, analytic truths. Now, I have no objection to the notion of conceptual truth as such. Perhaps, as is often alleged, ‘Bachelors are unmarried’ indeed expresses such a truth. Let us concede that it is true in virtue of our concept of a bachelor, or in virtue of what we take the word ‘bachelor’ to mean. But notice that ‘Bachelors are unmarried’ very plausibly has a quite different modal status from an essential truth such as, for example, ‘Cats are composed of matter’. In calling the former a ‘necessary’ truth, we cannot mean to imply that bachelors cannot marry, only that they cannot marry and go on rightly being called ‘bachelors’. The impossibility in question is only one concerning the proper application of a word. But in calling ‘Cats are composed of matter’ a necessary truth, we certainly can’t be taken to mean merely that cats cannot cease to be composed of matter and go on rightly being called ‘cats’ — as though the very same thing that, when composed of matter, was properly called a ‘cat’ might continue to exist as something immaterial. No: we must be taken to mean that cats cannot fail to be composed of matter simpliciter, that is, without qualification. Cats are things such that, if they exist at all, they must be composed of matter. The impossibility of there being an immaterial cat is not one that merely concerns the proper application of a word: it is, rather, a genuinely de re impossibility. That, I contend, is because it is one grounded in the essence of cats, inasmuch as it is part ofthe essence of a cat, as a living organism, to be composed of matter. In contrast, it is not part of the essence of any bachelor to be unmarried, for a bachelor is just an adult male human being who happens to be unmarried — and any such human being undoubtedly can marry. So, it seems clear, ‘Cats are composed of matter’ is certainly not a mere conceptual truth, and the same goes for other truths that are genuinely essential truths — truths concerning or grounded in the essences of things. They have, in general, nothing to do with our concepts or our words, but rather with the natures of the things in question. Of course, since concepts and words are themselves things of certain sorts, there can be truths concerning their essences. Indeed, what we could say about ‘Bachelors are unmarried’ is that it is, or is grounded in, a truth concerning the essence of the concept bachelor, or of the word ‘bachelor’. We could say, thus, that it is part of the essence of the concept bachelor that only unmarried males fall under it, and part of the essence of the word ‘bachelor’ that it applies only to unmarried males.

20 In any case, it is relatively easy to think of other examples of necessary truths which, even less (...) 20At this point, I anticipate the following possible response from the conceptualist, challenging my attempt to distinguish between the modal status of the statements ‘Bachelors are unmarried’ and ‘Cats are composed of matter’. Both statements, the conceptualist may say, express conceptual truths, and the difference between them lies only in the fact that, while the term ‘cat’ is a so-called substance sortal, the term ‘bachelor’ is only a phase sortal (for this distinction, see [Wiggins 2001, 28-30]). This, he may say, adequately explains why it makes no sense to suppose that something, by ceasing to be composed of matter, could cease to qualify as a cat and yet go on existing — for a substance sortal is precisely a term that, by definition, applies to something, if it applies to it all, throughout that thing’s existence. To this I respond as follows. We need to ask, crucially, what determines whether or not a given general term should be deemed to be a substance sortal. If this is taken simply to be a matter of what concept it expresses for speakers of the language in question, rather than a matter of what manner of thing it applies to, then deeply anti-realist consequences immediately ensue. To see this, suppose that there is a community of speakers who speak a language very like English in most ways, except that in place of the term ‘bachelor’ they deploy the term ‘sbachelor’, where ‘sbachelor’ in their language is (supposedly) a substance sortal rather than a phase sortal, so that they would deem ‘Sbachelors are unmarried’ to be on a par, modally, with ‘Cats are composed of matter’ — the implication being that, for these speakers, a sbachelor ceases to exist if he undergoes a marriage ceremony and is replaced by a numerically different being, called (let us say) a ‘shusband’. So, where ordinary English speakers would describe a certain situation as being one in which a certain man survives the transition from being a bachelor to being a husband, speakers of our imaginary community would instead describe the very same situation as being one in which a certain sbachelor ceases to exist and is replaced by a shusband. As far as I can see, the conceptualist cannot say that we ordinary English speakers describe this situation rightly and that the imagined speakers describe it wrongly: for the only standard of correctness to which the conceptualist can appeal is that provided by the actual conceptual repertoire of the speakers of any given language. That being so, since the two speech communities clearly differ over the question as to whether or not, in the envisaged situation, something has ceased to exist, the conceptualist seems committed to the conclusion that there is no mind-independent fact of the matter concerning such existential questions — and this position is blatantly anti-realist.

21But I said that conceptualism is ultimately incoherent. Indeed, I think it is. For one thing, as we have just seen, the proper thing to say about ‘conceptual’ truths is, very plausibly, that they are grounded in the essences of concepts. That being so, the conceptualist cannot maintain, as he does, that all putative facts about essence are really just facts concerning concepts. For this is to imply that putative facts about the essences ofconcepts are really just facts concerning concepts of concepts — and we have set out on a vicious infinite regress. No doubt the conceptualist will object that this complaint is question-begging. However, even setting it aside, we can surely see that conceptualism is untenable. For the conceptualist is at least committed to affirming that concepts — or, in another version, words — exist and indeed that concept-users do, to wit, ourselves. These, at least, are things that the conceptualist must acknowledge to have identities, independently of how we conceive of them, on pain of incoherence in his position. The conceptualist must at least purport to understand what a concept or a word is, and indeed what he or she is, and thus grasp the essences of at least some things. And if of these things, why not of other kinds of things? Once knowledge of essences is conceded, the game is up for the conceptualist. And it must be conceded, even by the conceptualist, on pain of denying that he or she knows what anything is, including the very concepts that lie at the heart of his account. For, recall, all that I mean by the essence of something is what it is.

22I recognize, however, that conceptualism is deeply entrenched in some philosophical quarters and that conceptualists are consequently unlikely to relinquish their views very readily in the light of objections of the sort that I have just raised. Hence, in the remaining two sections of this paper, I shall endeavour to undermine conceptualism in two further ways: first, by exposing the unholy alliance between conceptualism and scepticism and, second, by developing a more general argument to show how conceptualism leads to global anti-realism and why it is ultimately incoherent.

23Why is anyone ever even tempted by conceptualism, if it has such deep flaws as I maintain? My own view is that this temptation is the legacy of scepticism, particularly scepticism concerning ‘the external world’. The sceptic feels at home with himself and with his words and concepts, but expresses doubt that we can ever really know whether those words and concepts properly or adequately characterize things in the external world. He thinks that we can know nothing about how or what those things are ‘in themselves’, or indeed even whether they are many or one. According to the sceptic, all that we can really know is how we conceive of the world, or describe it in language, not how it is. But by what special dispensation does the sceptic exclude our concepts and our words from the scope of his doubt? For are they not, too, things that exist? There is, in truth, no intelligible division that can be drawn between the external world, on the one hand, and us and our concepts and our language on the other. Here it may be protested: But how, then, can we advance to a knowledge of what and how things are ‘in themselves’, even granted that the sceptic is mistaken in claiming a special dispensation with regard to the epistemic status of our concepts and our words? However, the fundamental mistake is to suppose, with the sceptic, that such an ‘advance’ would have to proceed from a basis in our knowledge of our concepts and words — that is, from a knowledge of how we conceive of and describe the world — to a knowledge of that world ‘as it is in itself’, independently of our conceptual schemes and languages. This ‘inside-out’ account of how knowledge of mind-independent reality is to be acquired already makes such knowledge impossible and must therefore be rejected as incoherent.

24But what alternative is there, barring a retreat to some form of anti-realism? Again, knowledge of essence comes to the rescue. Because, in general, essence precedes existence, we can at least sometimes know what it is to be a K — for example, what it is to be a material object of a certain kind — and thereby know, at least in part, what is or is not possible with regard to Ks, in advance of knowing whether, or even having good reason to believe that, any such thing as a K actually exists. Knowing already, however, what it is whose existence is in question and that its existence is at least possible, we can intelligibly and justifiably appeal to empirical evidence to confirm or cast doubt upon existence claims concerning such things. By ‘empirical evidence’ here, be it noted, I emphatically do not mean evidence constituted purely by the contents of our own perceptual states at any given time, as though all that we had to go on is how the world in our vicinity looks or otherwise appears to be. That, certainly, is not the conception of ‘empirical evidence’ that is operative in scientific practice, which appeals rather to the results of controlled experiments and observations, all of which are reported in terms of properties and relations of mind-independent objects, such as scientific instruments and laboratory specimens. The growth of objective knowledge consists, then, in a constant interplay between an a priori element — knowledge of essence — and an a posteriori element, the empirical testing of existential hypotheses whose possibility has already been anticipated a priori. This process does not have a foundational ‘starting point’ and it is constantly subject to critical reappraisal, both with regard to its a priori ingredients and with regard to its empirical contributions. Here we do not have a hopeless ‘inside-out’ account of objective knowledge, since our own subjective states as objective inquirers — our perceptions and our conceptions — are accorded no special role in the genesis of such knowledge. Those subjective states are merely some amongst the many possible objects of knowledge, rather than objects of a special kind of knowledge which supposedly grounds the knowledge of all other things. But, to repeat, it is crucial to this account that knowledge of essences is not itself knowledge of objects or entities of any kind, nor grounded in any such knowledge — such as knowledge of our own concepts.

25Recall that ‘conceptualism’, as I am using this term, is the view that, to that extent that talk about essences is legitimate at all, essences are purely conceptual in character. On this view, the essence of a kind of entities K is simply constituted by ‘our’ concept of a K — or, if not by ‘our’ concept, then at least by some thinking being’s concept. But what exactly is a ‘concept’ ? Well, ‘concept’ in the current context is a philosophical term of art, so it is partly up to us as philosophers to stipulate how we propose to use it. As I have already indicated, I myself regard a concept as being a way ofthinking ofsome thing or things, and I take it that conceptualists can agree with me about this. However, as a metaphysical realist, I also want to say that not all of our ways of thinking of things — not all of our conceptions of things — are equally good. Because I am a metaphysical realist, I believe that our conceptions of things may be more or less adequate, in the sense that they may more or less accurately reflect or represent the natures — that is, the essences — of the things of which we are thinking, or at least attempting to think. Thus it is open to me to stipulate further that, in my usage, a ‘concept’ is precisely an adequate conception of some thing or things, which accurately reflects the nature or essence of the things in question. For example, I can say that a child who conceives of a triangle merely as being a three-sided shape does not yet fully grasp the concept of a triangle, as a planar figure with three rectilinear sides. Clearly, however, it is not then open to me to say that the essence of Ks is constituted by our concept of a K, because this would leave no room for me to say, non-vacuously, that the concept of a K is a conception of Ks that accurately reflects the essence of Ks. Essences, on my account, must be mind-independent, if the question can sensibly be put as to whether or not a conception of Ks adequately reflects the essence of Ks. But what can be said on behalf of the rival view — conceptualism as I call it — that essences are always constituted by concepts? First, it should be clear, if it isn’t clear already, that conceptualism is a strongly anti-realist view. Second, I want to press home my complaint that conceptualism is a view that is ultimately incoherent. Let us deal with the first point first.

26The following question, it seems to me, must be a deeply embarrassing one for the conceptualist: in virtue of what, according to conceptualism, can it truly be said that there exist entities that fall under, or satisfy, our concepts — including, most centrally, our sortal or individ-uative concepts? That is to say, what does it take for there to be Ks, on this view? This is simple enough, it may be replied: there must be entities that possess whatever features they are that we have built into our concept of a K. So, for example, if K is lump of bronze, conceived, let us say, as a maximal connected aggregate of bronze particles, then there must be just such things. This will be the case if, sometimes, some bronze particles adhere to one another so as to form a maximal connected whole. Well and good: but remember that conceptualism is the doctrine that all essences are constituted by concepts. So, in particular, the doctrine must be taken to extend to the essence of bronze particles — what it is to be a bronze particle. (It must also extend to the essence of the relation of adherence, but I won’t dwell on that equally important fact for the moment, for the concept of adherence is not an individuative concept.) Bronze particles, on this view, exist just in case there are some things that possess whatever features we have built into our concept of a bronze particle. However, either the concept of a bronze particle is relevantly similar to that of a lump of bronze, in that it characterizes the nature of such an entity in terms of properties and relations of entities of other kinds, or it is not. If it is, then the next question is just pushed back one stage. If it is not — and this is the next question — then what does it take for the world to contain entities falling under the concept? What, in this case, must the world contribute to the fact that entities of this putative kind exist? Since, according to conceptualism, all essences are constituted by concepts — where concepts are understood to be ‘ways of conceiving deployed by thinkers — the conceptualist cannot suppose that how the world is, in respect of what kinds of entities it contains, is something that is the case independently of what concepts thinkers deploy. On this view, what it is for the world to contain entities of a kind K just is for the concept of a K to have application, or be applicable. Consequently, an adherent of this view cannot cash out what it is for such a concept to have application in terms of there being in the world entities answering to the concept. For, as I say, on this view, there being in the world such entities just is a matter of the concept s ‘having application’. So a quite different understanding of ‘having application’ must at least implicitly be in play.

27What is this alternative understanding? I think that it can only be something like this: the concept of a K ‘has application just in case thinkers find it useful, or convenient, to conceive of the world as containing Ks. This may require the concept in question to be logically consistent — thus ruling out, for example, the applicability of such concepts as 'round square cupola — but otherwise the constraints would seem to be purely pragmatic. This, it seems clear, is a deeply anti-realist view. It is a view according to which, in Hilary Putnam’s well-known words, there isn’t a ‘ready-made world’ [Putnam 1983] — or, if you like, there isn t any truth about ‘what is there anyway , to use Bernard Williams’s equally familiar phrase [Williams 1978, 64]. Or, yet again, it is a view according to which, to employ Michael Dummett’s somewhat less felicitous metaphor, reality is an ‘amorphous lump — one that can be ‘sliced up’ in indefinitely many different but equally legitimate ways, depending on what ‘conceptual scheme we or other thinkers happen to deploy [Dummett 1981, 563]. It may also be the view to which David Wiggins is committed, willy-nilly, by the doctrine that he calls ‘concep-tualist realism — committed in virtue of the fact that the only notion of individuation that he admits is a cognitive one, whereby individuation is a singling out of objects by thinkers [Wiggins 2001, 6]. Not only is this view deeply anti-realist: it is also, as I have said, doubtfully coherent. For those who philosophize in these terms rarely stop to think about how their doctrine is supposed to accommodate thinkers, their thoughts, and the concepts that they deploy. For these, too, are putative kinds of entities, whose essences, according the conceptualist doctrine, must like all others be constituted by ‘our concepts of them. It is at this point that the conceptualist manifestly paints himself into a corner from which there is no escape. There simply is no coherent position to be adopted according to which all essences are constituted by concepts, because concepts themselves are either something or else nothing — they either exist or they do not. If they don t, then conceptualism is out of business. But if they do, then they themselves have an essence — what it is to be a concept. The conceptualist, to be consistent, must say that the essence of concepts is constituted our concept of a concept. But what could this mean? And what could it mean, according to conceptualism, to say that the concept of a concept ‘has application — that there are concepts? I don t believe that conceptualism has any intelligible answer to such questions. The lesson, I take it, is that at least some essences must be mind-independent, in a way that conceptualism denies. Serious essentialism, as I call it, is my attempt to provide such an account of essence.