Natural deduction

Common card · No. 341137

In logic and proof theory, natural deduction is a kind of proof calculus in which logical reasoning is expressed by inference rules closely related to the "natural" way of reasoning, such as introducing temporary assumptions (to introduce an "if") or reasoning by cases (to eliminate an "or"). This contrasts with Hilbert-style systems, which instead use axioms as much as possible to express the logical laws of deductive reasoning.

Read on Wikipedia