postulator vs avower

postulator and avower both are nouns.

Word	Noun	Adjective	Verb	Adverb
postulator	Yes	No	No	No
avower	Yes	No	No	No

As nouns, avower is a hypernym of postulator; that is, avower is a word with a broader meaning than postulator:

postulator: someone who assumes or takes something for granted as the basis of an argument
avower: someone who claims to speak the truth

Other hypernyms of postulator include affirmer, asserter, asseverator, declarer.

postulator (noun)	avower (noun)
someone who assumes or takes something for granted as the basis of an argument	someone who admits or acknowledges openly and boldly
(Roman Catholic Church) someone who proposes or pleads for a candidate for beatification or canonization	someone who claims to speak the truth