Freedom and practical reason › How duty discloses freedom

Kant explains the relation between freedom and the moral law with two Latin expressions. Freedom is the ratio essendi, the ground of being, of the moral law. The moral law is the ratio cognoscendi, the ground of knowing, of freedom. The expressions concern two different directions of dependence.

Freedom makes moral legislation possible. But awareness of the moral law is what gives us practical warrant for recognizing freedom. We do not have to establish freedom through theoretical observation before we can recognize duty. The demand itself directs attention to a capacity that cannot be understood simply as following whichever inclination is strongest.

Kant's threatened-witness example clarifies this thought. A person may be uncertain whether fear would overcome them. Nevertheless, when they recognize that they ought to refuse false testimony, they also judge refusal possible. Uncertainty about their courage is compatible with recognition of an obligation.

The example does not establish that people invariably do what duty requires. Its force depends on keeping obligation distinct from a prediction of behavior. If we inferred freedom only from impressive resistance, timid agents would lack access to the argument. Kant locates the connection in consciousness of what should be done, even when someone doubts that they will do it.