Consider the classical conception of atoms in a vacuum in a box - the perfect gas; they collide and it this impulse of force that is their only interaction; and thus their dynamics; and this comes from the impenetrability of matter.

For if they were not impenetrable; one atom would pass through another; and there could be no collision; thus no impulse of force.

But no impressed force implies no change in motion (Newtons first law); but more precisely given that motion is change, we say there is no motion; that is it is at rest (Aristotles Physics).

And in this world let us switch off impenetrability; thus atoms can pass through each other; and no force is ever exerted; thus all atoms are at rest.

Interestingly this picture reminds me of the Parmenidian One in which there is no real motion (and thus motion is only apparent - or perhaps relative).

But is there anything in this?


Yes, the original atomic theory, usually attributed to Leucippus and Democritus, was formed in part as a response to Parmenides' arguments against the reality of movement, and to the related paradoxes of Zeno's. The Democratic atom possesses some of the properties of the Parmenidian One: It is neither created, nor destroyed. It also never changes, intrinsically, but only in relations to other atoms. One could say that while Parmenides rejected the reality of relations altogether, Democritus made them the basis of contingency and movement, keeping intrinsic properties fixed.


Antitypia or impenetrability as a defining property for matter has been known since antiquity. It was revived in early modern times notably by Leibniz who was aware that the new mechanical science is not without intrinsic difficulties. Newtonian mechanics readily uses 'material points' which is not an obvious construct. How could different masses be ascribed to zero-dimensional objects? How many of these objects can be present at the same point of space? Heavy point-like particles interact gravitationally in classical physics and they have of course impulses and energy. But the details are usually elsewhere.

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