(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"
(psychology) a theory that reduces all mental phenomena to simple elements (sensations and feelings) that form complex ideas by association
any personal belief about how to live or how to deal with a situation; "self-indulgence was his only philosophy"; "my father's philosophy of child-rearing was to let mother do it"
the rational investigation of questions about existence and knowledge and ethics
(medicine) the act of caring for someone (as by medication or remedial training etc.); "the quarterback is undergoing treatment for a knee injury"; "he tried every treatment the doctors suggested"; "heat therapy gave the best relief"