… the Good and Being are indeed interchangeable and why the Euthyphro dilemma fails.Not according to Plato:
"Therefore, say that what provides the truth to the things known and gives the power to the one who knows, is the idea of the good. And, as the cause of the knowledge and truth, you can understand it to be a thing known; but, as fair as these two are—knowledge and truth—if you believe that it is something different from them and still fairer than they, your belief will be right. As for knowledge and truth, just as in the other region it is right to hold light and sight sunlike, but to believe them to be sun is not right; so, too, here, to hold these two to be like the good is right, but to believe that either of them is the good is not right. The condition which characterizes the good must receive still greater honor." (508e-509 a)Various philosophers have distinguished between Being and beings, but Plato is making a different distinction, between being and becoming, the intelligible and physical realm, Form and image, eternal unchanging and temporal changing.
“Therefore, say that not only being known is present in the things known as a consequence of the good, but also existence and being are in them besides as a result of it, although the good isn't being but is still beyond being, exceeding it in dignity and power.” (509b)
There is an ambiguity and play of images with regard to the idea (eidos or form) of the Good, but that is a discussion for another time. I will only touch on a few key points. Socrates indicates the problem here:
“... So tell what the character of the power of dialectic is, and, then, into exactly what forms it is divided; and finally what are its ways. For these, as it seems, would lead at last toward that place which is for the one who reaches it a haven from the road, as it were, and an end of his journey."Socrates gives an image of the Good as it “looks” to him. The look of a thing is the eidos of that thing (look is one of the terms that defines and translates eidos). The Form of the Good as presented by Socrates is an image of the Good given in speech. He goes on:
"You will no longer be able to follow, my dear Glaucon," I said, "although there wouldn't be any lack of eagerness on my part. But you would no longer be seeing an image of what we are saying, but rather the truth itself, at least as it looks to me. Whether it is really so or not can no longer be properly insisted on. But that there is some such thing to see must be insisted on. Isn't it so?"
"And, also, that the power of dialectic alone could reveal it to a man experienced in the things we just went through, while it is in no other way possible?"What is important to note here is that Plato is now explicitly rejecting the notion of mystical transcendence. If the Good itself can be known it is only through dialectic, that is, reason. But, as the divided line makes clear, reason is not capable of grasping the Forms themselves. So, both the way of mystical transcendence and dialectic are rejected. This should not be surprising given Socrates skepticism. This skepticism is shared by Plato, and that is why the dialogues often end in aporia.
So, for Plato not only is it not true that Good and Being are interchangeable, but that the Good itself is unknown and appears to be an image of Plato’s philosophical poetry.
The “Euthyphro dilemma” does not fail. The question of right action, of justice and piety remain even if one defines God differently that Euthyphro does. In addition, the underlying problem of the presumption of knowledge of divine things remains.