Contingency: A characteristic of finite things that exist but do not exist necessarily. Those who support the cosmological argument believe that the contingency of the natural order shows that it must have its ground of existence outside itself and that the ultimate ground for the existence of contingent things must be a being whose existence is not contingent but necessary -- a being identifiable as God. 1
1. C.Stephen Evans, Pocket Dictionary of Apologetics & Philosophy of Religion (Downers Grove, IL: InterVarsity Press, 2002), p. 113.