The Cartesian theory of the passions forms the bridge over which its author passes from psychology to ethics. No soul is so weak as to be incapable of completely mastering its passions, and of so directing them that from them all there will result that joyous temper advantageous to the reason. The freedom of the will is unlimited. Although a direct influence on the passions is denied it,--it can neither annul them merely at its bidding, nor at once reduce them to silence, at least, not the more violent ones,--it still has an indirect power over them in two ways. During the continuance of the affection (e.g., fear) it is able to arrest the bodily movements to which the affection tends (flight), though not the emotion itself, and, in the intervals of quiet, it can take measures to render a new attack of the passion less dangerous. Instead of enlisting one passion against another, a plan which would mean only an appearance of freedom, but in fact a continuance in bondage, the soul should fight with its own weapons, with fixed maxims _(judicia)_, based on certain knowledge of good and evil. The will conquers the emotions by means of principles, by clear and distinct knowledge, which sees through and corrects the false values ascribed to things by the excitement of the passions. Besides this negative requirement, "subjection of the passions," Descartes' contributions to ethics--in the letters to Princess Elizabeth on human happiness, and to Queen Christina on love and the highest good--were inconsiderable. Wisdom is the carrying out of that which has been seen to be best, virtue is steadfastness, sin inconstancy therein. The goal of human endeavor is peace of conscience, which is attained only through the determination to be virtuous, i.e., to live in harmony with self.