Reading Russell's Why I Am Not a Christian I stumbled upon a passage (The Moral Arguments for Deity) I don't seem to understand.
Kant, as I say, invented a new moral argument for the existence of God, and that in varying forms was extremely popular during the nineteenth century. It has all sorts of forms. One form is to say there would be no right or wrong unless God existed. I am not for the moment concerned with whether there is a difference between right and wrong, or whether there is not: that is another question. The point I am concerned with is that, if you are quite sure there is a difference between right and wrong, then you are in this situation: Is that difference due to God's fiat or is it not? If it is due to God's fiat, then for God himself there is no difference between right and wrong, and it is no longer a significant statement to say that God is good. If you are going to say, as theologians do, that God is good, you must then say that right and wrong have some meaning which is independent of God's fiat, because God's fiats are good and not bad independently of the mere fact that he made them. If you are going to say that, you will then have to say that it is not only through God that right and wrong came into being, but that they are in their essence logically anterior to God.
I marked the sentence that is of interest to me. What is Russell's argument here and where does this conclusion come from? Can you point out the hidden premises? Is the claim that, if God decided between possibility A and B and decided to do A, that he could have done otherwise and that there is no inherent qualitative difference between A and B before his decision?