1. (

• atomism ,

) (psychology) a theory that reduces all mental phenomena to simple elements (sensations and feelings) that form complex ideas by association ;

2. (

• atomism ,
• atomic_theory ,
• atomist_theory ,
• atomistic_theory

) (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" ;