|Atom: in philosophy indivisible, possibly only assumed object. Not empirical, but argumentative.|
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Individuals may be no atoms. - Atoms would all be identical because they have the same parts (i.e. none).
Atomless/Mereology: e.g. the open sets of a Euclidean space - deep question: whether the mereology is atomistic or atomless. - Atomless: E.g. continua in the space-time, space time regions, etc. - mathematically: discrete - but not perceptual.
Atomless mereology: points, lines, etc. are not part of specific individuals (bodies, "events", etc.) in which they lie. - (Aristotle, Whitehead)
Phenomena/Leibniz: are atomless - monads: atoms = Atomism/Mereology/Simons: an individual is part of another iff. all the atoms of the first are atoms of the second. - (Instead SSP) -> identity condition for individuals: if they have the same atoms.
Parts Oxford New York 1987