¹ All references to Locke's Essay Concerning Human Understanding are to Peter Nidditch's edition (Oxford: Clarendon Press, 1975)Google ScholarPubMed. References are given by book, chapter and section number.

² A Letter to the Right Reverend Edward, Lord Bishop of Worcester, Concerning Some Passages Relating to Mr. Locke's Essay of Human Understanding (London, 1690Google Scholar; reprinted in The Works of John Locke, Darmstadt: Scientia, 1963, vol. 4), 26Google Scholar.

³ Locke maintains that the abstract idea of a kind is what ‘every days experience furnishes us with’ (II.xxiii.28). The phrase ‘every days experience’ might appear to refer to folk theories, but Locke's nominal essence should be seen to include even the most advanced theoretical characterization. Note that according to Locke, one cannot possibly acquire ‘a perfect Science of natural Bodies, (not to mention spiritual Beings)’ (IV.iii.29). Even the most advanced science cannot reveal the true nature of things. Nominal essence is grounded in not only folk theories but also professional theories, whether physical or psychological.

⁴ Kim, Han-Kyul, ‘What Kind of Philosopher was Locke on Mind and Body’, Pacific Philosophical Quarterly 9 (2010), 180–207CrossRefGoogle Scholar.

⁵ Some commentators take the phrase ‘besides’ as implying a bare particular: ‘the Substance is supposed always something besides the Extension, Figure, Solidity, Motion, Thinking, or other observable Ideas, though we know not what it is’. The so-called bare substratum reading explains the in-principle unknowability by reference to the nature of substratum per se, such that it has nothing to know about (since it is property-less) (For example, Bennett, Jonathan, Locke, Berkeley, Hume: Central Theme (Oxford: Oxford University Press, 1971Google Scholar)). In my view, this sort of explanation of why one is incurably ignorant about it has distorted the principle of the ‘Modesty of Philosophy’, wherein Locke obviously refers to the internal reason that our ideas are inadequate to reality. Throughout the Essay, Locke explains the reason we are incurably ignorant about intrinsic property of things themselves by reference to the ideas one has of them, rather than any specific nature of things such as their bareness or nakedness. No epistemic modesty exists in the bare substratum account; there is nothing unknowable about a bona fide intrinsically bare substratum.

⁶ The following passages can be taken as examples that indicate these nominal or functional definitions: ‘The primary Ideas we have peculiar to body, as contra-distinguished to Spirit, are the cohesion of solid, and consequently separable parts, and a power of communicating motion by impulse’ (II.xxiii.17); ‘The Ideas we have belonging, and peculiar to Spirit, are Thinking, and Will, or a power of putting Body into motion by Thought, and, which is consequent to it, Liberty’ (II.xxiii.18).

⁷ Elsewhere, I have proposed a functionalist account of substratum: ‘The Supposed Unknown: A Functionalist Account of Locke's Substratum’, in Lodge, Paul and Stoneham, Tom (eds), Locke and Leibniz on Substance (London: Routledge, 2014)Google Scholar. In the functionalist reading, the substratum is not identified with a particular constitution of the insensible particles but a functional entity, such that whatever plays the role of ‘uniting’ a bundle of qualities – regularly co-exhibited – counts as the substratum of an individual substance. I have also argued that Locke applied this functionalist account to any sort of substance, whether mental or physical, or whether ordinary-sized object or insensible particles.

⁸ Kim, Jaegwon, Philosophy of Mind (Third edition, Westview Press, 2011), 134Google Scholar.

⁹ Woolhouse, Roger (ed.), John Locke's Debate with Edward Stillingfleet, Bishop of Worcester, as it figures in footnote in the Fifth Edition of the Essay (London: Penguin, 1997), 690Google Scholar.

¹⁰ Moreover, Locke considers a sort of multiplicity on the nominality side, depending on the possible creation scenario where the creator could create different intellectual species' having wholly different sets of perceptual/conceptual devices. Locke regards the human mind as a natural kind, and one of ‘many Species of Spirits’. This remark is made in the Essay, Book III, Chapter vi, where Locke makes the distinction between nominal and real essence. Locke's inventory of mental natural kinds includes both these lower kinds and the higher kinds, such as angels: ‘There are different Species of Angels; yet we know not how to frame distinct specifick Ideas of them’ (III.vi.11). Each mental kind is endowed with its own perspective on the world. Each species produces a different type of nominal essence about the same world, and human knowledge is but one sort among many. However, the mere existence of many perspectives would not necessarily constitute the reason for why our intellectual devices are inadequate to the intrinsicity of the world. Hence, the multiplicity of species per se would not strongly explain the incurable sort of ignorance. The substantial reason for his humility lies in the multiplicity placed on reality, not on nominality.

¹¹ Lewis, David, ‘Ramseyan Humility’, in Braddon-Mitchell, David and Nola, Robert (eds.), Conceptual Analysis and Philosophical Naturalism (MIT Press, 2009), 207Google Scholar.

¹² I take this example from Jaegwon Kim, op. cit., 170.

¹³ A Dictionary of Physics, Oxford Paperback Reference (Oxford: Oxford University Press, 1996), 121Google ScholarPubMed.

¹⁴ Priestley, Joseph, Disquisitions Relating to Matter and Spirit (London, 1777; reprinted by Garland Publishing 1976), 8Google Scholar.

¹⁵ Ibid., 5.

¹⁶ Ibid.

¹⁷ Langton, Rae, Kantian Humility: Our Ignorance of Things in Themselves (Oxford: Oxford University Press, 1998), Chapter 2Google Scholar.

¹⁸ In accounting for the ground of the Kantian humility, Langton remarks: ‘While [the humility] is partly because of receptivity, it is also partly because it is not through things as they are in themselves that we are affected – it is not through the intrinsic properties of things that we are affected, since [Kant] thinks (as he puts it in another early work) that ‘substance never has the power, through its own intrinsic properties, to determine others different from itself’ [Kant 1922b: 415]' (‘Elusive Knowledge of Things in Themselves’, Australasian Journal of Philosophy 82 (2004), 133Google Scholar). If the term ‘power’ here means a real potency irreducible to the intrinsic property of a substance, then Lockean humility should be differentiated from this Kantian humility.

¹⁹ Mr. Locke's Reply to the Right Reverend the Lord Bishop of Worcester's Answer to his Second Letter (London, 1699; reprinted in The Works of John Locke, vol. 4), 469Google Scholar.

²⁰ Ibid.

²¹ A Letter to the Right Reverend Edward, Lord Bishop of Worcester, Concerning Some Passages Relating to Mr. Locke's Essay of Human Understanding, 33.