Every other candidate for unconditional goodness fails under scrutiny. Intelligence sharpens the plans of a villain. Courage steadies the hand of a murderer. Even happiness, when possessed by someone whose will is corrupt, is an affront to the moral observer. These qualities are good only conditionally — only when governed by a will that is itself good. The good will alone requires no such condition.
Kant insists that the good will's worth is entirely independent of what it accomplishes. Should misfortune or nature's stinginess prevent it from achieving any of its aims, it would not thereby be diminished. Like a jewel, it shines by its own light. Results and outcomes belong to the world of cause and effect; moral worth belongs to the will alone.
If happiness were nature's purpose for us, instinct would have served far better than reason, which so often leads us away from contentment. Kant infers from this that reason's true purpose is not to produce happiness but to produce a will that is good in itself — a will worthy of happiness. This reframing of reason's role is the hinge on which all of Kant's ethics turns.
The concept of the good will opens the First Section of the Groundwork and provides the foundation from which Kant derives the entire structure of his moral philosophy.
