presuppose vs posit

presuppose is not a noun while posit is a noun.

Word	Noun	Adjective	Verb	Adverb
presuppose	No	No	Yes	No
posit	Yes	No	Yes	No

As verbs, posit is a hyponym of presuppose; that is, posit is a word with a more specific, narrower meaning than presuppose:

Other hyponyms of presuppose include postulate, premise, premiss.

presuppose (noun)	posit (noun)
	(logic) a proposition that is accepted as true in order to provide a basis for logical reasoning

presuppose (verb)	posit (verb)
require as a necessary antecedent or precondition	take as a given; assume as a postulate or axiom
take for granted or as a given; suppose beforehand	put before
	put (something somewhere) firmly