"When any opinion leads to absurdity, it is certainly false; but it is not certain that an opinion is false because it is of dangerous consequence."--(IV. p. 112.)
And, therefore, that the attempt to refute an opinion by a picture of its dangerous consequences to religion and morality, is as illogical as it is reprehensible.
It is said, in the first place, that necessity destroys responsibility; that, as it is usually put, we have no right to praise or blame actions that cannot be helped. Hume's reply amounts to this, that the very idea of responsibility implies the belief in the necessary connexion of certain actions with certain states of the mind. A person is held responsible only for those acts which are preceded by a certain intention; and, as we cannot see, or hear, or feel, an intention, we can only reason out its existence on the principle that like effects have like causes.
If a man is found by the police busy with "jemmy" and dark lantern at a jeweller's shop door over night, the magistrate before whom he is brought the next morning, reasons from those effects to their causes in the fellow's "burglarious" ideas and volitions, with perfect confidence, and punishes him accordingly. And it is quite clear that such a proceeding would be grossly unjust, if the links of the logical process were other than necessarily connected together. The advocate who should attempt to get the man off on the plea that his client need not necessarily have had a felonious intent, would hardly waste his time more, if he tried to prove that the sum of all the angles of a triangle is not two right angles, but three.
A man's moral responsibility for his acts has, in fact, nothing to do with the causation of these acts, but depends on the frame of mind which accompanies them. Common language tells us this, when it uses "well-disposed" as the equivalent of "good," and "evil-minded" as that of "wicked." If A does something which puts B in a violent passion, it is quite possible to admit that B's passion is the necessary consequence of A's act, and yet to believe that B's fury is morally wrong, or that he ought to control it. In fact, a calm bystander would reason with both on the assumption of moral necessity. He would say to A, "You were wrong in doing a thing which you knew (that is, of the necessity of which you were convinced) would irritate B." And he would say to B, "You are wrong to give way to passion, for you know its evil effects"--that is the necessary connection between yielding to passion and evil.