It is a principle so simple and rational that it can be found in a children’s book. I remember reading “Is Your Momma a Llamma” a hundred times. Each page manifests more and more that scholastic axiom that the way a thing acts manifest the way that it exists. It is amazing to think how much of science is based on this simple principle. Consider the very way that physics is done and how we come to conclusion about the thing itself from its behavior.
I was thinking about this when my brother asked me about how we know that a brute is actually a brute and doesn’t have the same sort of intelligence as a human, just in a lesser degree. The simple response is to insist on an empirical study. Does a dog, cat or other animal act rational? Does it appear to deliberate? Does it consider things as they are in themselves? If not, then we have no reason to be it exists as a rational animal because it doesn’t act like a rational animal.
This brings me back again to the question of whether an artifact is a substance. The thing to ask is for a empirical investigation. All substances attempt to preserve themselves in their being this kind of substance. You have to smash atoms together very hard to get something different. Animals will fight back if you try to kill them. Etc. Now, does a mousetrap try to preserve its “mousetrap-ness”? Does it resist being changed qua mousetrap? Does the hammock made of vines preserve itself qua hammock? It does not appear so. The hammock in particular will tend toward preserving itself qua vines if it is alive and easily breakdown if it is dead unless maintained extrinsically.