If the meaning and purpose of reason as an instrument of knowledge converges to the possibility of discernment involving the true and the false, which is necessary to the exercise is nothing but a method that involves the application of certain provisions intended both to understanding how the will, whose contradiction characterizes the metaphysical ground of mistake, according to Descartes, as noted in that article, uses a doubt, the absolute foundations of research, contains a radical which tends to stop at the borders of the act of doubting himself, who implies the experience of the Cogito and brings the ontological proof of God's existence as a single condition, to ensure the reality of the world.