Abstract

When I classify Fluffy as a cat, I appear to do so out of an appreciation of a prior metaphysical fact, namely, that she has a nature or essence common to creatures we classify as cats. Locke turns this picture on its head. Our actual practices of naming and sorting individuals into kinds proceed according to ideas in the mind. As Locke puts it, species (kinds) are ‘the Workmanship of the Understanding,’ not the workmanship of nature, because their essences consist in abstract ideas, or ‘nominal essences,’ we make. Many take Locke to mean that the observable similarities and differences between things leave it undetermined how we are to group and distinguish them, so that classification is, and must be, a matter of convention. And while Locke never denies that individuals have real essences, it is argued that knowledge of them would not reveal natural boundaries, either. On this influential reading, nature does not draw boundaries between kinds, and she makes this fact apparent to us. I argue that Locke’s claim that nature does not determine the ‘Boundaries of the Species of Things’ should be understood as the claim that nature does not draw the variable boundaries set out in the nominal essences we make. Differences in our nominal essences reflect differences in speakers’ knowledge of external ‘standards,’ which we latch on to by way of their ‘leading’ qualities, which present the mind with a limited number of unique and highly salient bases for classification. On my reading, nature may very well draw boundaries of her own.