I have come across a dilemma, I could not find the question on the site presently so I hope it has not been answered yet. If an atom is the smallest piece of matter that we are aware of, doesn't some form of matter have to make up an atom? And whatever the form of matter that makes up an atom, would have to be made up of some other form of matter and that matter would have to be made up of a kind of matter as well, and on and on forever. Where does that stop? How can a human being ever comprehend something like this? Thank you.

This is a wonderfully knotty question that has occupied philosophers at least since Zeno of Elea in the 5th century BCE. One way of interpreting Zeno on this is to say that the problem shows that space is illusory. David Hume later, like the atomists ('atom' meaning uncuttable) seems to have thought that there must be a point at which the cutting stops, at least so far as the world of experience goes. I might say that Zeno is right that certain ways of conceiving space are flawed, including the way the problem as you pose it conceives of space--that is, as continuous all the way down, becoming just a finer and finer Cartesian grid if you will, always subject to the same sorts of properties or ways of conceiving things (like length, height, depth, etc.). It seems, however, that once we reach the sub-atomic realm these ways of conceiving things just don't hold, so that it becomes impossible to apply mathematical divisions of space. Space seems dependent on, you might say, the ability of energy to propagate and knot in various ways and as we approach quarks (which have perhaps no spatial dimensions) it simply is not able to do so. So, in a sense the atomists are right but not because there is finally an uncuttable (or indivisible) particle, either conceptually or really. Rather, they're right because after a certain point the idea of cutting becomes in applicable.

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