unbelief vs mental object

unbelief and mental object both are nouns.

Word	Noun	Adjective	Verb	Adverb
unbelief	Yes	No	No	No
mental object	Yes	No	No	No

As nouns, mental object is a hypernym of unbelief; that is, mental object is a word with a broader meaning than unbelief:

unbelief: a rejection of belief
mental object: the sum or range of what has been perceived, discovered, or learned

Other hypernyms of unbelief include cognitive content, content.

unbelief (noun)	mental object (noun)
a rejection of belief	the sum or range of what has been perceived, discovered, or learned