Out of the dim reminiscence of such views there finally arose Kant's doctrine of the Autonomy of the Will, which, as the mouth-piece of Pure, Practical Reason, lays down the law for all rational beings as such, and recognises nothing but =formal= motives, as opposed to =material=; the latter determining only the lower faculty of desires, to which the higher is hostile. For the rest, this whole theory, which was not really systematically set forth till the time of Descartes, is nevertheless to be found as far back as Aristotle. In his _De Anima_ I. 1, it is sufficiently clearly stated; while Plato in the _Phaedo_ (pp. 188 and 189, edit. Bipont.) had already paved the way, with no uncertain hints. After being elaborated to great perfection by the Cartesian doctrine, we find it a hundred years later waxed bold and strong, and occupying the foremost place; but precisely for this reason forced to reveal its true nature. An excellent _résumé_ of the view which then prevailed is presented in Muratori's _Della Forza della Fantasia,_ chaps. 1-4 and 13. In this work the imagination is regarded as a purely material, corporeal organ of the brain (the lower faculty of perception), its function being to intuitively apprehend the external world on the data of the senses; and nought remains for the immaterial soul but thinking, reflecting, and determining. It must have been felt how obviously this position involves the whole subject in doubt. For if Matter is capable of the intuitive apprehension of the world in all its complexity, it is inconceivable that it should not also be capable of abstracting this intuition; wherefrom everything else would follow. Abstraction is of course nothing else than an elimination of the qualities attaching to things which are not necessary for general purposes, in other words, the individual and special differences. For instance, if I disregard, or abstract, that which is peculiar to the sheep, ox, stag, camel, etc., I reach the conception of ruminants. By this operation the ideas lose their intuitiveness, and as merely abstract, non-intuitive notions or concepts, they require words to fix them in the consciousness, and allow of their being adequately handled. All this shows that Kant was still under the influence of the after-effect of that old-time doctrine, when he propounded his Practical Reason with its Imperatives.