Herbert McCabe on natural kinds
I do not know how to give an account of the way we have come to divide up our experienced world into what John Locke would have called ‘natural kinds’ or natural units; it is evidently an extremely important part of the business of living with things and interacting with them in all sorts of ways. It seems to me that the idea that we are completely free to reclassify the objects of experience in just any way at all, or (what is the same thing) to use just any names at all to express what is to be a unit in our world, rests on the idea that we are simply spectators of something that stands over against us called the ‘world’, and we are at liberty to put just any kind of grid we like between the world and our eyes. In fact we are not just spectators, we are involved with and have to cope with things. And recognizing the natural units is part of coping. […]
We distinguish true from false statements by living in our world and talking with others in our world, arguing and so on. We could call this ‘experience’ had not the word been hijacked by empiricists who imagine that experience is simply being hit by sense-data.
from On Aquinas, (Continuum, 2008), 10-11, 22.