In opposition to Aristotle, for whom practical reason differs from theoretical reason solely in the end toward which it directs its theoretical knowledge, Kant means by practical reason the capacity to determine an act unconditionally, that is, freely. Since the Kantian doctrine of determinants is based on a conception of mutual relation between practical reason and volition, this study traces the development, progressive clarification, and precise result of his thought from the Grundlegung zur Metaphysik der Sitten to the Metaphysik der (...) Sitten.... Identification of practical reason with the will in the notion of autonomy guides research on the objective determining ground.... The article investigates the source from which Kant derived his notion of a determining ground and the role which analogy to natural activity played in its development [abr, tr fr j by PCS]. (shrink)