Introduction: Inferences and Proofs

Most of the time, logic is said to be the science of correct reasoning. However, this definition is only apparently simple. According to a long-standing tradition, stemming from Descartes, a reasoning is a chain of steps leading from hypotheses to conclusions. Indeed, Descartes says in Regulae that a proof is a continuous and uninterrupted movement of thought in which each individual proposition is clearly intuited. (in Cottingham,