Talk of “essences” has, since Saul Kripke and Hilary Putnam, gained significant currency in contemporary philosophy. It is no longer unfashionable to talk about the essence of this or that (natural) kind, and as such we now find a variety of brands of essentialism on the market including B.D. Ellis’s scientific essentialism, David Oderberg’s real Essentialism, Alexander Bird’s dispositional essentialism, and the contemporary essentialism of Kripke and Putnam.
Almost all these brands of essentialism share a particular gloss on Locke’s famous objection to Aristotle that natural kinds are demarcated by nominal essences not real essences. Thus Oderberg claims that ‘Empiricists take [real] essences to be paradigmatically unobservable’ and that this ‘objection goes back at least to John Locke’ (Oderberg 2007: 21). Bird, presenting his dispositional essentialism, defines a notion of “being” as ‘the reverse of Locke’s definition of essence’ which he takes to be ‘the being of any thing, whereby it is what it is’ (Bird 2007: 100). Joseph LaPorte, discussing nominal and real essences, claims that ‘Kripke and Putnam seem to affirm something more substantive: that biological kinds have “real essences” in Locke’s terminology’ (LaPorte 2004: 49). Even avowed anti-essentialists such as John Dupré sanction the standard criticism of Locke that his scepticism about the knowability of real essences was ‘premature’, and claim that ‘genuine natural kinds provide the extensions of many terms of natural language, where these natural kinds are determined by true Lockean real essences’ (Dupré 1993: 22).
All of these essentialisms (even Dupré’s anti-essentialism) are wrong about Locke. Oderberg is wrong to claim that Locke thought that real essences were paradigmatically unobservable; Bird is wrong to think that Locke’s notion of essence is the being of anything whereby it is what it is; LaPorte is wrong to think that Kripke and Putnam are talking about Lockean real essences (although so are Kripke and Putnam); and Dupré is wrong to think that genuine natural kinds (if by genuine he means objective or mind-independent) are determined but true Lockean real essences .
The mistake stems from a standard, but ultimately incorrect, interpretation of Locke’s discussion of essences in An Essay Concerning Human Understanding . This mistaken interpretation (Lowe 1995, 2006, Von Leyden 1973, Wiggins 1974) takes Locke to mean, by “real essence”, the Aristotelian notion i.e. ‘the very being of anything, whereby it is what it is’ (Essay III.iii.15), and interprets his objection as epistemological: we cannot come to know what real essences are, and therefore they cannot figure in our classifications of things into kinds.
This paper will present and defend the following two claims: i) that Locke’s notion of “real essence” is not the Aristotelian notion, and ii) that Locke’s objection to the Aristotelian notion was not merely epistemological. The first claim can be defended by presenting and applying Vienne’s (1993) terminological revision. Vienne argues that Locke did not introduce a dichotomy between real and nominal essence, but a trichotomy between real essence, nominal essence and real constitution. This terminological revision will be employed to highlight where ambiguous uses of the phrase “real essence” have caused some serious misunderstandings of Locke’s philosophy. The second claim (steering Locke around what is the classic objection to his thesis) can be defended by presenting a novel way of splitting up Locke’s objections to the Aristotelian notion of essence. The analysis will show that Locke’s anti-essentialism is still in good shape, and of contemporary significance.