Atomism remains the paradigm for physical explanations:
There are only atoms and the void within which they move. And the All is made up of their collisions and their combinations.
In this picture, an atom retains its identity. It is it's own self at this time and for all time. An atom is an everlasting element of reality.
Aristotle however argued against this picture. He suggested a thought experiment: what happens if two atoms collide, at the moment of collision are their surfaces in touch with other?
Now, if at this moment the two atoms are seperated by some distance, then they haven't yet collided. So there must be no distance between the two surfaces. But then, at this moment, what right have we to call them two distinct atoms?
This suggests that at this moment atoms lose there identity. But this self-identity is part of defining property of an atom. They are permanent.
It seems we have a contradiction. This either atoms cannot be as they are generally described. At best, sometimes they lose their identity. At worst, it's altogether the wrong picture. It may also suggest that fundamental ground of reality has no self-identity.
What is interesting here, is that in QFT, particles do appear to lose identity: particle number is not conserved.
I'm using the picture of atoms as described first by Democritus. But in the contemporary world atoms are not described as such. They are also the locus of a field. For example, the electron is the source of an EM field. (One might argue, that it is in fact the field, that as a whole is fundamental, and the sources within it are mere parts and so derived).
Can Aristotles argument be made to work in such a context? That is with atoms that are the source of forces, and it is these forces that either attract or repel them?