philosophical theory vs ism

philosophical theory and ism both are nouns.

Word	Noun	Adjective	Verb	Adverb
philosophical theory	Yes	No	No	No
ism	Yes	No	No	No

As nouns, ism is a hypernym of philosophical theory; that is, ism is a word with a broader meaning than philosophical theory:

philosophical theory: a doctrine accepted by adherents to a philosophy
ism: a belief (or system of beliefs) accepted as authoritative by some group or school

Other hypernyms of philosophical theory include doctrine, philosophical system, philosophy, school of thought.

philosophical theory (noun)	ism (noun)
a doctrine accepted by adherents to a philosophy	a belief (or system of beliefs) accepted as authoritative by some group or school