Good thoughts!

So before grouping it into use-units, you actually need to create whatever you want to categorize.

A lot of it comes pre-created for us by nature. Let's say you meet with a new object. First thing you notice is it has shape and size. Why do you notice that? Because if you don't and you walk toward it, you might hurt your leg, say. Plants don't have vision because they don't move fast enough. Sense of touch is more appropriate in their case, because they're so slow that if there's any distance between you and them, it's like you're not there.

So first you see the object and its shape and size and colors (could be poisonous) etc. This comes by nature. The rest is more a result of nurture and more in line with what you've said.

Your response of course merits further thought and commenting. It's true everything is very fluid. You can never step into the same river twice and all that. What makes the river the same river? Its usefulness to us is the same. The atoms that make us up change every day, but Monday-Tom and Tuesday-Tom have equal usefulness to his wife and children etc. Reality's constant change has been troubling philosophers for millennia, hopefully this idea of "use" can explain somewhat how we give (lasting) identities to objects.

Again, not doing justice to what you said exactly, which is about "nothingness/emptiness" and all that, but it's rather late so I'll end it here!

Thanks for reading!