Abstract

If the task of theoretical reason is to discover truth, or reasons for belief, then theoretical reason is impossible. Attempts to circumvent that by appeal to probabilities are self-defeating. If the task of practical reason is to discover what we ought to do or what actions are desirable or valuable, then practical reason is impossible. Appeals to the subjective ought or to subjective probabilities are self-defeating. Adapting Karl Popper, I argue that the task of theoretical reason is to obtain theories that we can agree to instate given that they appear to have greater explanatory merit than their rivals. I then argue that the task of practical reason is to decide which ought-propositions to act on. As a consequence theoretical reason is seen as a branch of practical reason. This approach makes both theoretical and practical reason practicable and free of the defects of the usual accounts.