1. The great problem of Moral Philosophy is the explanation of the idea, _I ought_, (c. i., n. 6). We are now come close up to the solution of that problem. The word _ought_ denotes the necessary bearing of means upon end. To every _ought_ there is a pendent _if_. The means _ought_ to be taken, _if_ the end is to be secured. Thus we say: "You _ought_ to start betimes, _if_ you are to catch your train." "You _ought_ to study harder, _if_ you are to pass your examination." The person spoken to might reply: "But what if I do miss my train, and fail in my examination?" He might be met with another _ought_: "You _ought_ not to miss the one, _if_ you are to keep your appointment: or to fail in the other, _if_ you are to get into a profession." Thus the train of _oughts_ and _ifs_ extends, until we come finally to a concatenation like the following: "You _ought_ not to break your word, or to give needless pain to your parents, _if_ you don't want to do violence to that nature which is yours as a reasonable being," or "to thwart your own moral development,"--and so on in a variety of phrases descriptive of the argument of the last section. Here it seems the chain is made fast to a staple in the wall. If a person goes on to ask, "Well, what if I do contradict my rational self?" we can only tell him that he is a fool for his question. The _oughts_, such as those wherewith our illustration commenced, Kant calls the _hypothetical imperative_, the form being, "You must, unless:" but the _ought_ wherein it terminated, he calls the _categorical imperative_, the alternative being such as no rational man can accept, and therefore no alternative at all. 2. This doctrine of the Categorical Imperative is correct and valuable so far as it goes. But then it does not go far enough. The full notion of what a man _ought_, is what he _must do under pain of sin_. Sin is more than folly, more than a breach of reason. It is mild reproach to a great criminal to tell him that he is a very foolish person, a walking unreasonableness. If he chooses to contradict his rational self, is not that his own affair? Is he not his own master, and may he not play the fool if he likes? The answer is, "No, he is not his own master; he is under law, and his folly and self-abuse becomes criminal and sinful, by being in contravention of the law that forbids him to throw himself away thus wantonly."