In the introduction to the Metaphysic of Morals, Kant distinguishes between the empirical and the rational mode of treating Ethics. He announces his intention to depart from the common plan of mixing up the two together, and to attempt for once to set forth the _pure_ moral philosophy that is implied even in the vulgar ideas of duty and moral law. Because a moral law means an absolute necessity laid on all rational beings whatever, its foundation is to be sought, not in human nature or circumstances, but _à priori_ in the conception of pure reason. The most universal precept founded on mere experience is only a practical rule, and never a moral law. A purely rational moral philosophy, or Metaphysic of Morals, will serve the double end of meeting a speculative requirement, and of furnishing the only true norm of practice. It investigates the idea and principles of a potentially pure Will, instead of the acts and conditions of human volition as known from psychology. Not a complete Metaphysic of Morals, however, (which would be a Critique of the pure Practical Reason), but merely a foundation for such will be given. The supreme principle of morality is to be established, apart from detailed application. First, common notions will be analyzed in order to get at this highest principle; and then, when the principle has been sought out, they will be returned upon by way of synthesis. In the first of the three main sections of the work, he makes the passage from Common Rational Knowledge of Morals to Philosophical. Nothing in the world, he begins, can without qualification be called good, except _Will_. Qualities of temperament, like courage, &c., gifts of fortune, like wealth and power, are good only with reference to a good will. As to a good will, when it is really such, the circumstance that it can, or cannot, be executed does not matter; its value is independent of the utility or fruitlessness of it.