supposition

guess, speculation, surmisal, surmise, conjecture, hypothesis

opinion, view - a message expressing a belief about something; the expression of a belief that is held with confidence but not substantiated by positive knowledge or proof; "his opinions appeared frequently on the editorial page"

divination - successful conjecture by unusual insight or good luck

supposal, assumption

conclusion - an intuitive assumption; "jump to a conclusion"

cornerstone, fundament, groundwork, basis, foundation, base - the fundamental assumptions from which something is begun or developed or calculated or explained; "the whole argument rested on a basis of conjecture"

hypothesis, theory, possibility - a tentative insight into the natural world; a concept that is not yet verified but that if true would explain certain facts or phenomena; "a scientific hypothesis that survives experimental testing becomes a scientific theory"; "he proposed a fresh theory of alkalis that later was accepted in chemical practices"

given, presumption, precondition - an assumption that is taken for granted

basic assumption, constatation, self-evident truth - an assumption that is basic to an argument

supposal

conjecture - reasoning that involves the formation of conclusions from incomplete evidence

presupposition - the act of presupposing; a supposition made prior to having knowledge (as for the purpose of argument)