Categorical imperative requires reason to dictate the act we are morally obligated to do, one which is motivated by adherence to the consistent principle which could be applied to all and any rational agent. This deontological ethical distinguishes between the moral doctrines of right from that of virtue. Where the first is driven externally to the actor, the other is internal and concerned with ends.
Circumscribing what end is - Kant required of a rational human being that he makes the object of his elective will his end. Kant is very much concerned with ends which at the same time are duties and not with ends due to impulses of the senses or subjective/technical ends. The former are for him objective/moral ends and rests on a priori principles.
For Kant, a rational human being is a moral person, fully conscious of his moral duty or duties and deriving deliberate decisions using the metaphysical moral framework. The mere possession of capacity for rationality is nothing compared to its exercise and fulfillment in action.
All of this is built upon the foundation of good will or universal good or good unqualified/unconditional and autonomous which he laid down in Groundwork. ...