The Unity of the Principle of Contradiction in Leibniz

Rodriguez-Pereyra (2013) points to at least six different principles referred to as the principle of contradiction in Leibniz and states: “The texts suggest that on different occasions he used ‘Principle of Contradiction’ [PC] to refer to different principles. This is puzzling, given the subtlety and power of Leibniz’s mind, for it suggests that he did not really distinguish between the different versions of the principle”. Rodriguez-Pereyra himself suggests that the “different principles” are versions of the PC, as they are all principles which exclude true contradiction and serve to ground mathematical and necessary truths but thinks that it needs to be spelled out more clearly how it is possible that differing principles are one principle, without Leibniz taking note of this. The present paper builds on Rodriguez-Pereyra’s and shows that the various formulations of the PC are indeed different because they amount to different logical contents. However, I shed light on their unity and argue that the different logical contents are expressions of one epistemic principle, which I argue is the PC.