The Formal Elenchos Appearing in the Principle of Non-Contradiction

Aristotle states that the deductive process cannot prove the ‘principle’, i.e., ‘truth’, because deduction takes truth as a given. The principle, called the ‘Principle of Non-Contradiction’ (PNC), can only be proved by a new kind of demonstration: elenchos. The PNC is considered as undeniable because its negation ends up negating itself. We note that the negation that is internal to the principle, because it is essential to its constitution, must be determined in order not to be the negation of nothing. However, what determines it is precisely the contradiction, so that the PNC apparently excludes the contradiction, but in fact requires it precisely in order to deny it.