In short, Moore does not simply contradict himself once again by saying that nothing can be substituted for “good” and then by providing a synonym at the same time, but compounds the contradiction, by giving several synonyms. Moreover, what makes things worse, is that the synonyms he provides each have a proper and consistent meaning: none can be analytically reduced to another without sounding absurd (even if a synthetic relation is conceivable). It is as if we were told that the word “giraffe” has four synonyms: “cat”, “leg”, “chair”, and “interest”.

In chapter 1, Moore implicitly confounds the concepts of good and duty, when he answers an objection, raised by the hedonist, which consists in saying that the concept of good may be an empty shell.
[the hedonist speaks:] Most people have used the word [good] for what is pleasant and for what is desired respectively.
[Moore’s answer:] Nor do I think that [he] would be willing to allow that this was all he meant. They are all so anxious to persuade us that what they call the good is what we really ought to do. Do, pray, act so, because the word good is generally used to denote actions of this nature: such, on this view, would be the substance of their teaching. And in so far as they tell us how we ought to act, their teaching is truly ethical, as they mean it to be ¹.

This means that the controversy existing between Moore and the hedonist is not simply verbal as they both agree that the word “good” means “what we ought to do” (duty). However, they differ over whether the concept of duty may be reduced to that of pleasure or whether it is distinct therefrom.
Anyway, Moore affirms that the concept of good contains the concept of duty, although we have seen that, in his opinion, the simple notion of good is unanalyzable.

Two other occurrences may be noted.
Firstly, in chapter 2: If [these theories were] true, they would simplify the study of Ethics very much. They all hold that there is only one kind of fact, of which the existence has any value at all. But they [all consider] that the main reason why the single kind of fact they name […] is that it has been held to define what is meant by good itself ². Moore admits here that “good in itself” is equivalent to the concept of “existence has value”.

Secondly, in chapter 5, he shows that if we want to define what we ought to do, we have to determine what action, in a given situation, produces the most value, in itself, and in its effects, or (as if it were equivalent), produces the most good: We must have all this causal knowledge, and further we must know accurately the degree of value both of the action itself and of all these effects
[…] And not only this: we must also possess all this knowledge with regard to the effects of every possible alternative; and must then be able to see by comparison that the total value due to the existence of the action in question will be greater.
But it is obvious that our causal knowledge alone is far too incomplete for us ever to assure ourselves of this result, that an action is our duty: we can never be sure that any action will produce the greatest value possible.
Ethics, therefore, is quite unable to give us a list of duties: but there still remains a humbler task which may be possible for Practical Ethics […] there may be some possibility of shewing which among the alternatives, likely to occur to any one, will produce the greatest sum of good ³.

Here again, value, good, and duty, are confounded.

1. Ibid., chap. 1, §11
2. Ibid., chap. 2, §24
3. Ibid., chap 5, §91