You talk about something’s “very nature”. I reject that concept. It is a form of reification, and I reject all forms of reification.
I disagree. I don’t think it is reification at all, for reasons I will address below.
You are creating two things, the hammer and the ‘nature of the hammer’. If things all have a nature, then you also have ‘the nature of the nature of the hammer’ and so on in an infinite regress. There is a hammer. Just a hammer. A piece of metal with a handle. It is an error to see extra things, like a ‘nature’ or an ‘essence’ sitting behind the hammer. Those extra things are not part of the hammer, but are added by our brains as part of the process of perception and analysis.
Au contraire! You are creating one thing: the hammer. The nature of the hammer is an immaterial part as well as a necessary condition of the hammer (see my response to your next statement.) In even conceding that such a thing as a hammer exists, you are ascribing unto it a nature. A “hammer” is a real thing. A real thing whose purpose is to exert highly concentrated force to other objects; usually nails. Are we justified in saying that this is the nature of the hammer? Yes. Why? Because that is the known objective for which it was created. It may be used for other things, certainly, but its primary purpose is well known and universally agreed upon.
Even if we were to accept that what I have been doing is a fallacy of reification, you would then be guilty of commiting the same fallacy yourself. How so? By defining a hammer. You say it is a piece of metal (which, admittedly, is objective and detached enough so far) with a handle. But why a handle? Why is it a handle and not just a long piece of wood? Why is it wood and not just a certain arrangements of atoms? It is wood because you know that wood is a collection of atoms with certain properties; a nature. It is a handle because you know it is intended to be gripped. A hammer did not just appear out of nowhere, it was created for a purpose.
On the other hand, if you were to define it as simply “a piece of metal with a long piece of wood attached,” you create an obvious falsehood. Not just any piece of metal with a long piece of wood attached would be accepted as a hammer. Hammers have distinctive proportions that govern their ability to fulfill their purpose. Anything else is just a piece of wood and a stick; not a hammer at all. You might call it a hammer, but then I might call myself a whale. It doesn’t make it so, unless you reject all definitions out of hand, in which case discourse of any kind is pointless.
But ultimately, the point is that if there were no “intrinsic nature” to a hammer, then human beings couldn’t even conceive of one to create it. The nature precedes the object; not the other way around.
An arachnophobe seeing a spider will also sense fear. That fear is not part of the spider, but is something added by the arachnophobe. Similarly with the ‘nature’ of the hammer. It is additional to the hammer, not part of the hammer.
This is total conflation. The arachnophobe’s fear is obviously something within themselves; it is a reaction to the object. Nor is it “added” to the spider. Noone, not even your hypothetical arachnophobe, if asked to objectively describe the natural purpose of a spider would include invoking fear in that list, unless they were jesting or seriously lacked the ability to distinguish between their feelings and the things that provoke them.
This is not the same with the hammer. The nature of the hammer is not added to it after the fact of its creation; it is the very conceptual reality that gave rise to the invention of the hammer. Man didn’t just stumble upon a hammer and then feel a sudden impulse to drive a nail or break a rock. He desired to drive a nail or break a rock and created a hammer to do so.