Full Idea
The principle of contradiction is the principle of necessity, and the principle that a sufficient reason must be given is the principle of contingency.
Gist of Idea
Necessities rest on contradiction, and contingencies on sufficient reason
Source
Gottfried Leibniz (On Sufficient Reason [1686], p.95)
Book Reference
Leibniz,Gottfried: 'Leibniz Selections', ed/tr. Wiener,Philip P. [Scribners 1951], p.95
A Reaction
[this paragraph is actually undated] Contradictions occur in concrete actuality, as well as in theories and formal systems. If so, then there are necessities in nature. Are they discoverable a posteriori? Leibniz says not.
Related Idea
Idea 19661 Making sufficient reason an absolute devalues the principle of non-contradiction [Hegel, by Meillassoux]