Will is also under the necessity of doing what it ought; he means that what it ought to do means nothing but its own law—the law according to which it must act. It differs from the human will just in that, what we ought to do, is what it necessarily does. It is ‘autonomous’; and by this is meant (among other things) that there is no separate standard by which it can be judged: that the question ‘Is the law by which this Will acts a good one?’ is, in its case, meaningless. It follows that what is necessarily willed by this Pure Will is good, not because that Will is good, nor for any other reason; but merely because it is what is necessarily willed by a Pure Will.
Kant’s assertion of the ‘Autonomy of the Practical Reason’ thus has the very opposite effect to that which he desired; it makes his Ethics ultimately and hopelessly ‘heteronomous.’ His Moral Law is ‘independent’ of Metaphysics only in the sense that according to him we can know it independently; he holds that we can only infer that there is Freedom, from the fact that the Moral Law is true. And so far as he keeps strictly to this view, he does avoid the error, into which most metaphysical writers fall, of allowing his opinions as to what is real to influence his judgments of what is good. But he fails to see that on his view the Moral Law is dependent upon Freedom in a far more important sense than that in which Freedom depends on the Moral Law. He admits that Freedom is the ratio essendi of the Moral Law, whereas the latter is only the ratio cognoscendi of Freedom. And this means that, unless Reality be such as he says, no assertion that ‘This is good’ can possibly be true: it can indeed have no meaning. He has, therefore, furnished his opponents with a conclusive method of attacking the validity of the Moral Law. If they can only shew by some other means (which he denies to be possible but leaves theoretically open) that the nature of Reality is not such as he says, he cannot deny that they will have proved his ethical principle to be false. If what ‘This ought be done’ means ‘This is willed by a Free Will,’ then, if it can be shewn that there is no Free Will which wills anything, it will follow that nothing ought to be done.
76. And Kant also commits the fallacy of supposing that
