- incredulity, disbelief, skepticism, mental rejection - doubt about the truth of something
--1 is a kind of doubt, uncertainty, incertitude, dubiety, doubtfulness, dubiousness
- unbelief, disbelief - a rejection of belief
--2 is a kind of content, cognitive content, mental object
--2 has particulars:agnosticism, skepticism, scepticism; atheism; heresy, unorthodoxy