Contingency is usually seen as the opposite of necessity – the idea that everything that has ever occurred and ever will occur is necessary and cannot be otherwise. In a necessary world there is no chance or contingency as everything is determined by the laws of nature. Possibility, too, includes necessity; if something is necessary, it is possible. On this view, contingency is merely a subset of possibility.

In many non-Western philosophies, post-structuralism, and information philosophy the world is seen as profoundly contingent as everything that exists – any being, thing, or event – could be, or could have been other than it is. On this view, the fundamental nature of reality is one of irreducible contingency while necessity is an invention of the human mind.