To be undecided about; to lack confidence in; to disbelieve, to question.
Disbelief or uncertainty (about something); (countable) a particular instance of such disbelief or uncertainty.
To take for granted; to conclude, with less than absolute supporting data; to believe.
To require to exist or to be true; to imply by the laws of thought or of nature.
To put by fraud in the place of another.
To theorize or hypothesize.
To imagine; to believe; to receive as true.