La Logique de Port-Royal is regarded by historians of this science as a treatise that does not fit into any of their categories; indeed, the art of Logic as an independent exercise of the mind seemed unacceptable to its authors. Writing at the end of the Aristotelian era and under the influence of Cartesian theories, but having their own convictions about man's nature and obligations, Antoine Arnauld and Pierre Nicole saw logical reasoning as justifiable only if it trains the mind to distinguish between Good and Bad. They believed in the existence of an immutable, eternal truth; man's reason is intended to make this Truth a perceivable reality. Logic, most importantly, therefore, trains our word-using and concept-making faculty to acknowledge that the needs of man's soul belong to a much higher order of values than the science of “things”: it should thus give reason the strength to be “true” to its own nature. (In French)