Hintikka set also called model set, downward saturated set, a set (of a certain sort) of well-formed formulas that are all true under a single interpretation of their non-logical symbols (named after Jaakko Hintikka). Such a set can be thought of as a (partial) description of a logically possible state of affairs, or possible world, full enough to make evident that the world described is indeed possible. Thus it is required of a Hintikka set G that it contain no atomic formula and its negation, that A, B 1 G if A 8 B 1 G, that A 1 G or B 1 G if A 7 B 1 G, and so forth, for each logical constant. See also POSSIBLE WORLDS, SET THE- OR. G.F.S.