Naïve and Metaphysical Realism, if they are to be consistent, have to deny freedom for one and the same reason, viz., because, for them, man does nothing but carry out, or execute, principles necessarily imposed upon him. Naïve Realism destroys freedom by subjecting man to authority, whether it be that of a perceptible being, or that of a being conceived on the analogy of perceptible beings, or, lastly, that of the abstract voice of conscience. The Metaphysician, content merely to infer an extra-human reality, is unable to acknowledge freedom because, for him, man is determined, mechanically or morally, by a "thing-in-itself." Monism will have to admit the partial justification of Naïve Realism, with which it agrees in admitting the part played by the world of percepts. He who is incapable of producing moral ideas through intuition must receive them from others. In so far as a man receives his moral principles from without he is actually unfree. But Monism ascribes to the idea the same importance as to the percept. The idea can manifest itself only in human individuals. In so far as man obeys the impulses coming from this side he is free. But Monism denies all justification to Metaphysics, and consequently also to the impulses of action which are derived from so-called "things-in-themselves." According to the Monistic view, man's action is unfree when he obeys some perceptible external compulsion; it is free when he obeys none but himself. There is no room in Monism for any kind of unconscious compulsion hidden behind percept and concept. If anybody maintains of the action of a fellow-man that it has not been freely done, he is bound to produce within the visible world the thing or the person or the institution which has caused the agent to act. And if he supports his contention by an appeal to causes of action lying outside the real world of our percepts and thoughts, then Monism must decline to take account of such an assertion. According to the Monistic theory, then, man's action is partly free, partly unfree. He is conscious of himself as unfree in the world of percepts, and he realises in himself the spirit which is free.