S: (v) guess, venture, pretend, hazard (put forward, of a guess, in spite of possible refutation) "I am guessing that the price of real estate will rise again"; "I cannot pretend to say that you are wrong"
S: (v) speculate (talk over conjecturally, or review in an idle or casual way and with an element of doubt or without sufficient reason to reach a conclusion) "We were speculating whether the President had to resign after the scandal"
S: (v) reason (think logically) "The children must learn to reason"
S: (v) think, cogitate, cerebrate (use or exercise the mind or one's power of reason in order to make inferences, decisions, or arrive at a solution or judgments) "I've been thinking all day and getting nowhere"