To explain what we mean by Good and Bad, we may say that a thing is good when on its own account it ought to exist, and bad when on its own account it ought not to exist. If it seems to be in our power to cause a thing to exist or not to exist, we ought to try to make it exist if it is good, and not exist if it is bad. When a thing is good, it is fitting that we should feel pleasure in its existence; when it is bad, it is fitting that we should feel pain in its existence. But all such characterizations really presuppose the notions of good and bad, and are therefore useful only as a means of calling up the right ideas, not as logical definitions. (§ 5 ¶ 1)

It might be thought that good could be defined as the quality of whatever we ought to try to produce. This would merely put ought in place of good as our ultimate undefined notion; but as a matter of fact the good is much wider that what we ought to try to produce. There is no reason to doubt that some of the lost tragedies of Aeschylus were good, but we ought not to try to re-write them, because we should certainly fail. What we ought to do, in fact, is limited by our powers and opportunities, whereas the good is subject to no such limitation. And our knowledge of goods is confined to the things we have experienced or can imagine; but presumably there are many goods of which we human beings have absolutely no knowledge, because they do not come within the very restricted range of our thoughts and feelings. Such goods are still goods, even though human conduct can have no reference to them. Thus the notion of good is wider and more fundamental than any notion concerned with conduct; we use the notion of good in explaining what right conduct is, but we do not use the notion of right conduct in explaining what good is. (§ 5 ¶ 2)