ever occurred was an act which the agent ought not to have done; and, if the "ought" is the one which implies "can," it implies, therefore, that every theft was an act which the agent, if he had chosen, could have avoided. And this statement that every theft which has been committed was an act which the thief, _if_ he had so willed, could have avoided, though it may be doubted if it is absolutely universally true, is not a statement which is clearly absurd, like the statement that every covetous desire could have been avoided by the will of the person who felt it. It is probable that the vast majority of acts of theft have been acts which it was in the power of the thief to avoid, if he had willed to do so; whereas this is clearly not true of the vast majority of covetous desires. It is, therefore, quite possible that those who believe we ought never to steal are using "ought" in a sense which implies that stealing always _could_ have been avoided; whereas it is I think quite certain that many of those who believe that we ought to avoid all covetous desires, do not believe for a moment that every covetous desire that has ever been felt was a desire which the person who felt it could have avoided feeling, if he had chosen. And yet they certainly do believe, in some sense or other, that no covetous desire _ought_ ever to have been felt. The conclusion is, therefore, it seems to me, unavoidable that we do use "ought," the moral "ought," in two different senses; the one a sense in which to say that I ought to have done so and so does really imply that I could have done it, if I had chosen, and the other a sense in which it carries with it no such implication. I think perhaps the difference between the two can be expressed in this way. If we express the meaning of the first "ought," the one which does imply "can," by saying that "I ought to have done so and so" means "It actually _was_ my duty to do it"; we can express the meaning of the second by saying that _e.g._ "I ought not to have felt so and so" means _not_ "it _was_ my duty to avoid that feeling," but "it _would_ have been my duty to avoid it, _if_ I had been able." And corresponding to these two meanings of "ought" we should, I think, probably distinguish two different sorts of moral rules, which though expressed in the same language, do in fact mean very different things. The one is a set of rules which assert (whether truly or falsely) that it always actually _is_ a duty to do or to refrain from certain actions, and assert therefore that it always is in the power of the agent's will to do or to refrain from them; whereas the other sort only assert that so and so _would_ be a duty, if it _were_ within our power, without at all asserting that it always is within our power.