contingent neither impossible nor necessary; i.e., both possible and non-necessary. The modal property of being contingent is attributable to a proposition, state of affairs, event, or – more debatably – an object. Muddles about the relationship between this and other modal properties have abounded ever since Aristotle, who initially conflated contingency with possibility but later realized that something that is possible may also be necessary, whereas something that is contingent cannot be necessary. Even today many philosophers are not clear about the ‘opposition’ between contingency and necessity, mistakenly supposing them to be contradictory notions (probably because within the domain of true propositions the contingent and the necessary are indeed both exclusive and exhaustive of one another). But the contradictory of ‘necessary’ is ‘non-necessary’; that of ‘contingent’ is ‘non-contingent’, as the following extended modal square of opposition shows:
These logicosyntactical relationships are preserved through various semantical interpretations, such as those involving: (a) the logical modalities (proposition P is logically contingent just when P is neither a logical truth nor a logical falsehood); (b) the causal or physical modalities (state of affairs or event E is physically contingent just when E is neither physically necessary nor physically impossible); and (c) the deontic modalities (act A is morally indeterminate just when A is neither morally obligatory nor morally forbidden).
In none of these cases does ‘contingent’ mean ‘dependent,’ as in the phrase ‘is contingent upon’. Yet just such a notion of contingency seems to feature prominently in certain formulations of the cosmological argument, all created objects being said to be contingent beings and God alone to be a necessary or non-contingent being. Conceptual clarity is not furthered by assimilating this sense of ‘contingent’ to the others.
See also MODAL LOGIC, NECESSITY. R.D.B.