Without going further into this, which may briefly indicate some of the perplexities involved, I may mention certain cases in which there seems to be a real divergence of the two principles. There are cases in which the temptation may be fairly held to lessen guilt, and in which punishment has, notwithstanding, been made severer in consequence. The criminal law of the last century, for example, imposed a penalty of death upon persons who stole certain kinds of property left in specially exposed positions. The ease of taking it would very possibly tempt to theft men who would elsewhere be honest; and it was sought to compensate for the strength of the temptation by more savage punishment of those who yielded to it. Or, again, there are certain problems of a similar kind connected with political offences. A man who gets up a rebellion from sincere political motives is generally far better morally than the man who gets up a rebellion for the sake, say, of simple plunder. Ought the motive to be allowed as an extenuation of the offence? It ought, it may be said, from a moral point of view; but, from the point of view of simple deterrence, we might rather consider that the patriotic rebel is the more dangerous person of the two, and, therefore, requires the prospect of at least as heavy a punishment to keep him quiet. So, again, it has been asked, whether it should be admitted as an excuse for a rioter, that he has joined in violent courses under threats from the riotous mob. This is, of course, an excuse from the moralist's point of view; the man is only attacking the police in order to save his own house from being burnt, not from a disorderly or disaffected spirit. But it is replied, from the deterring point of view, that, if such an excuse be allowed, you are ceasing to threaten at the precise moment when the threats are most required. If the law is not to press from one side, all the pressure will come from the other, and every argument will be in favour of joining the side of disorder. Hence, it is argued, we ought to proportion the punishment, not to the offence, but to the temptation.
Now, I may say, very briefly, that such a divergence of the two principles appears to me to be possible; and, further, that cases may be put in which it might be necessary to deter, at all hazards, even to the neglect of moral considerations. A general who is defending a town must sometimes burn the houses of innocent people, without stopping to consider whether they can ever be compensated; and I think that there may be analogous cases even in regard to law, where the consideration of the absolute necessity of putting down mischievous conduct may override the normal moral considerations. But the general answer is, I think, different, and may help to clear the principle. The law to which I have referred, for the protection of exposed property, obviously suggests one remark. The true remedy for the evil would have been not to increase the penalty, but to increase the protection. You ought to have provided more watchmen, or to have forbidden owners to put temptation in the way of their neighbours, and not to have tried to make the hangman do the work of the policeman. So our ancestors erred when they protected their fields, not by putting up fences, but by setting mantraps to mutilate occasional trespassers. In that, as in other cases, the mistake is to confuse between the deterring influence of punishment and the preventive influence of protective measures. Arguments, questionable when used on behalf of punishment considered as deterring, are perfectly applicable to the preventive measures. It is obviously right that such measures should be proportioned to the temptation. When a starving man steals a loaf, he is not so bad as a man who steals when he is not starving. We should, therefore, think it morally wrong to punish him as severely. But, if we thought that he ought not to have the loaf, we should take stronger precautions in proportion to the probable temptation. If, for example, we were sending supplies to relieve a starving district, it would be clearly right to send such a force with them as might prevent their appropriation by the strongest, or the first comers. But, at the same time, we should also think it right to save the men from temptation, by providing as much as possible against the danger of starvation. So, again, it would be monstrous to punish a poor man more severely than a duke, for stealing a watch; but, as a matter of prudence, I should take more precautions if I were dining in a poor public-house, than if I were dining in a ducal palace.