Source : Webster's Revised Unabridged Dictionary (1913)

Atomism \At"om*ism\, n. [Cf. F. atomisme.]
   The doctrine of atoms. See {Atomic philosophy}, under
   {Atomic}.

Source : WordNet®

atomism
     n 1: (psychology) a theory that reduces all mental phenomena to
          simple elements (sensations and feelings) that form
          complex ideas by association
     2: (chemistry) any theory in which all matter is composed of
        tiny discrete finite indivisible indestructible particles;
        "the ancient Greek philosophers Democritus and Epicurus
        held atomic theories of the universe" [syn: {atomic theory},
         {atomist theory}, {atomistic theory}] [ant: {holism}]