Principle of sufficient reason
Principle of sufficient reason
According to Leibniz, one of the two principles on which reasoning is founded, the other being the principle of Contradiction. While the latter is the ground of all necessary truths, the Principle of Sufficient Reason is the ground of all contingent and factual truths. It applies especially to existents, possible or factual, hence its two forms actual sufficient reasons, like the actual volitions of God or of the free creatures, are those determined by the perception of the good and exhibit themselves as final causes involving the good, and possible sufficient reasons are involved, for example, in the perception of evil as a possible aim to achieve. Leibniz defines the Principle of Sufficient Reason as followsIt is the principle “in virtue of which we judge that no fact can be found true or existent, no judgment veritable, unless there is a sufficient reason why it should be so and not otherwise, although these reasons cannot more than often be known to us. . . . There must be a sufficient reason for contingent truths or truths of fact, that is, for the sequence of things which are dispersed throughout the universe of created beings, in which the resolution into particular reasons might go into endless detail” (Monadology, 31, 32, 33, 36). And again, “Nothing happens without a sufficient reason; that is nothing happens without its being possible for one who should know things sufficiently to give a reason showing why things are so and not otherwise” (Principles of Nature and of Grace). It seems that the account given by Leibniz of this principle is not satisfactory in itself, in spite of the wide use he made of it in his philosophy. Many of his disciples vainly attempted to reduce it to the Principle of Contradiction. See Wolff.
2. Kant also developed the Leibnizian principles with some modifications in his early writing Principiorum Primorum Cognitionis Metaphysicae Nova Dilucidatio (1755), where the Principle of Sufficient Reason becomes the Principle of Determining Reason (Ratio Determinans). Two forms of this principle are distinguished by Kant the ratio cur or antecedenter determinans identified with the ratio essendi vel fiendi, and the ratio quod or consequenter determinans identified with the ratio cognoscendi. It has been defended under these forms against Crusius and the argument that it destroys human freedom. — T.G.