not in human nature or circumstances, but a 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.

This idea of the absolute worth of mere Will, though it is allowed even by the vulgar understanding, he seeks to establish beyond dispute, by an argument from the natural subjection of Will to Reason.  In a being well-organized, if Conservation or Happiness were the grand aim, such subjection would be a great mistake.  When Instinct could do the work far better and more surely, Reason should have been deprived of all practical function.  Discontent, in fact, rather than happiness comes of pursuit of mere enjoyment by rational calculation; and to make light of the part contributed by Reason to happiness, is really to make out that it exists for a nobler purpose.  But now, since Reason is a practical faculty and governs the will, its function can only be to produce a Will good in itself.  Such a Will, if not the only good, is certainly the highest; and happiness, unattainable by Reason as a primary aim, and subject in this life altogether to much limitation, is to be sought only in the contentment that arises from the attainment by Reason of its true aim, at the sacrifice often of many a natural inclination.