doctrine vs philosophical system

doctrine and philosophical system both are nouns.

Word	Noun	Adjective	Verb	Adverb
doctrine	Yes	No	No	No
philosophical system	Yes	No	No	No

As nouns, doctrine and philosophical system are synonyms defined as:

doctrine and philosophical system: a belief (or system of beliefs) accepted as authoritative by some group or school

Other synonyms of doctrine include ism, philosophy, school of thought.

doctrine (noun)	philosophical system (noun)
a belief (or system of beliefs) accepted as authoritative by some group or school	a belief (or system of beliefs) accepted as authoritative by some group or school