I think that this interpretation expresses a part of the meaning with which the words ‘ought’ and ‘duty’ are used in ordinary thought and discourse. For we commonly use the term ‘moral obligation’ as equivalent to ‘duty’ and expressing what is implied in the verb ‘ought,’ thus suggesting an analogy between this notion and that of legal obligation; and in the case of positive law we cannot refuse to recognise the connexion of ‘obligation’ and ‘punishment’: a law cannot be properly said to be actually established in a society if it is habitually violated with impunity. But a more careful reflection on the relation of Law to Morality, as ordinarily conceived, seems to show that this interpretation of ‘ought’--though it cannot be excluded--must be distinguished from the special ethical use of the term. For the ideal distinction taken in common thought between legal and merely moral rules seems to lie in just this connexion of the former but not the latter with punishment: we think that there are some things which a man ought to be compelled to do, or forbear, and others which he ought to do or forbear without compulsion, and that the former alone fall properly within the sphere of law. No doubt we also think that in many cases where the compulsion of law is undesirable, the fear of moral censure and its consequences supplies a normally useful constraint on the will of any individual. But it is evident that what we mean when we say that a man is “morally though not legally bound” to do a thing is not merely that he “will be punished by public opinion if he does not”; for we often join these two statements, clearly distinguishing their import: and further (since public opinion is known to be eminently fallible) there are many things which we judge men ‘ought’ to do, while perfectly aware that they will incur no serious social penalties for omitting them. In such cases, indeed, it would be commonly said that social disapprobation ‘ought’ to follow on immoral conduct; and in this very assertion it is clear that the term ‘ought’ cannot mean that social penalties are to be feared by those who do not disapprove. Again, all or most men in whom the moral consciousness is strongly developed find themselves from time to time in conflict with the commonly received morality of the society to which they belong: and thus--as was before said--have a crucial experience proving that duty does not mean _to them_ what other men will disapprove of them for not doing.