mental rejection vs incredulity

mental rejection and incredulity both are nouns.

Word	Noun	Adjective	Verb	Adverb
mental rejection	Yes	No	No	No
incredulity	Yes	No	No	No

As nouns, mental rejection and incredulity are synonyms defined as:

Other synonyms of mental rejection include disbelief, scepticism, skepticism.

mental rejection (noun)	incredulity (noun)
doubt about the truth of something	doubt about the truth of something