Leibniz proposed that demonstrations be reformulated as deductions from identities, and that propositions of the type A = A be the only source of truth. In this article, I aim to explain this theory of proof (and knowledge), as well as its elementary concepts, such as identity, truth (or possibility) and proposition (including Leibniz's theory of reducibility of propositions to subject-predicate form).
Proof; Identity; Reductio ad absurdum; Truth; Possibility; Leibniz