 We have seen that Locke’s particular substances are kinds of things, and because they are kinds they correspond to Aristotle’s secondary substances. But we have also seen that the boundaries between these kinds are largely a matter of convention, which is not true of Aristotle’s secondary substances. In so far as their individuation is dependent on human convention, they are not ultimately real in their own right. But though they are not real as kinds, the individual parcels of matter that we classify in these ways are perfectly real. Locke does not, as far as I can see, refer to these individuals as ‘substances’. Substances, considered as kinds, or instances of kinds, can sustain change—living things, for example, change in size throughout their lives. Most individual parcels of matter, however, become different individuals if they change any of their parts; although we have seen that this does not apply to living things, where there seems to be a metaphysical component called sameness of life.