Going through my head today for no good reason is a two-sentence passage of Dorothy Sayers', in an essay explaining some of the basic concepts of medieval scholastic philosophy, including "matter" and "form."
The sentence, which I'm quoting from memory, went something like this: "A cat is not simply a bunch of cat-stuff arranged in the form of a cat. Such a being exists, but its a dead cat."
She goes on to say that the difference between the dead and live cat is the latter's possession of certain faculties (of perception and nutrition): a living cat recognizes the world around it and feeds itself.
All of this reminds me, too, of a line in one of the Harry Potter books. One character has been killed through dark magic. The muggle police have found the body, and the coroners report that the body seems perfectly normal and healthy, excerpt for the fact that it is dead.
There is some sort of fallacy in the original Sayers passage that the HP passage seems to play off. Surely in the absence of magic something happens to stop a heart, and the something that happens shows up in an anatomical way, so that a coroner, even working on a cat's corpse, could come up with particular matters of form that are different now. And that explain those missing faculties.
There is a really profound thought here, just out of my reach.