The present paper brings a reading of Immanuel Kant's Critique of Practical Reason (1788), seeking support on two central axes: a) the formulation of the categorical imperative; b) the doctrine of the fact of reason. The choice of this course supports the position that, despite the innumerable formulations given to the imperative of morality throughout the GMS, there would be, in the terms of the second Critique, a clearer and more precise formulation of this principle. Regarding the doctrine of the fact of reason, it will be treated in two ways: on the one hand, from an attempt to reconstruct Kant's original theses, based on the philosopher's textual course; on the other, showing to what extent this doctrine represents a change of position...