philosophy vs aetiology

philosophy and aetiology both are nouns.

Word	Noun	Adjective	Verb	Adverb
philosophy	Yes	No	No	No
aetiology	Yes	No	No	No

As nouns, aetiology is a hyponym of philosophy; that is, aetiology is a word with a more specific, narrower meaning than philosophy:

philosophy: the rational investigation of questions about existence and knowledge and ethics
aetiology: the philosophical study of causation

philosophy (noun)	aetiology (noun)
the rational investigation of questions about existence and knowledge and ethics	the philosophical study of causation
a belief (or system of beliefs) accepted as authoritative by some group or school	the cause of a disease
any personal belief about how to live or how to deal with a situation