Kant first mentioned his plan to write “Metaphysical Foundations of Practical Philosophy” in a letter to Johann Heinrich Lambert on New Year's Eve, 1765. This work, for which Kant claimed to have already thought out the contents, would appear alongside a parallel “Metaphysical Foundations of Natural Philosophy.” Both were to function as introductions to Kant's newly devised “proper method of metaphysics” by providing “examples to show in concreto what the proper procedure should be.” Only after these “little essays” were published would Kant publish the denser work on method, which would then “not have to be burdened excessively with detailed and yet inadequate examples” (10:56).
As it turned out, not only did Kant abandon the plan to publish the illustrative works in practical and natural philosophy before the systematic work on method in metaphysics, spending much of the following decade and a half formulating that proper method and transforming the project until its culmination in the 1781 Critique of Pure Reason, he also wrote and published eight books and over a dozen essays – nearly the whole of his critical scholarly production – before finally returning to the work on a metaphysical foundations of practical philosophy over thirty years later. The Metaphysics of Morals is not itself identified as “metaphysical foundations,” though its two parts are: the Metaphysical Foundations of the Doctrine of Right and the Metaphysical Foundations of the Doctrine of Virtue.
The 210 pages of draft material for the Metaphysics of Morals in Volume 23 are third in quantity among drafts, exceeded only by the material for the Critique of Pure Reason and the incomplete and inchoate Opus Postumum. Three-quarters of this material is devoted to the Doctrine of Right, and about half of the remaining is aimed at the Introduction and Preface of the Doctrine of Virtue, prominently concerning the distinction between right and virtue. Generous selections from these drafts are included here.
Some other drafts were apparently inadvertently included in the published version of the Doctrine of Right.