The shopkeeper who charges every customer a fair price acts in conformity with duty. But if he does so only to maintain his reputation, his action has no moral worth. Similarly, the man who preserves his life, as duty requires, but does so simply because he enjoys living, acts correctly without deserving moral credit. Kant is not denying that such actions are fine — he is denying that they are morally praiseworthy.
An action done from duty derives its worth not from the outcome it produces, nor from the inclination that prompted it, but from the maxim — the principle — on which it was undertaken. When duty is the motive, the will is determined by a formal principle rather than by any desire for a particular result. This formality is precisely what elevates it.
What is the motive when one acts from duty, if not inclination and not expected outcome? Kant's answer is respect — a unique feeling that reason itself produces when it recognises the moral law. We cannot have respect for our inclinations, which we merely experience; we can have respect only for what overpowers inclination, for what commands regardless of what we happen to want. This is the law.
Kant develops these three propositions about duty in the First Section of the Groundwork, using them to arrive at the formulation of the categorical imperative from ordinary moral reasoning.
