postulate vs necessitate

postulate is a noun but necessitate is not a noun.

Word	Noun	Adjective	Verb	Adverb
postulate	Yes	No	Yes	No
necessitate	No	No	Yes	No

As verbs, postulate and necessitate are synonyms defined as:

Other synonyms of postulate include ask, call for, demand, involve, need, require, take.

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

postulate (verb)	necessitate (verb)
take as a given; assume as a postulate or axiom	require as useful, just, or proper
maintain or assert	cause to be a concomitant
require as useful, just, or proper