Plato’s moral realism

Notes for September 19

Main points

Today’s class served two purposes. I wanted to introduce our next topic: the status of moral beliefs. And I wanted to present one answer: moral realism. Plato is an excellent spokesman for this view.


The argument advanced in the dialog, Euthyphro raises trouble for theological voluntarism, the view that moral rules come from the will of a supernatural being.

Euthyphro had said that things are pious because the gods love them. Socrates, in turn, asked why the gods love what they do: is it because the things they love are pious or for some other reason?

This gives Euthyphro a dilemma. Suppose he takes the first alternative: the gods love pious things because they are pious. Then his explanation can’t be right: things would have to be pious before the gods love them; that’s their reason for finding those things more lovable than the rest.

By analogy, nothing is carried until someone picks it up and carries it. If nothing is pious until the gods love it, then the gods can’t start loving things because they are pious. That would be that would be like carrying things only because they are carried. Instead, the Gods would have to love pious things first. But then the fact that the things they love are pious couldn’t explain why they love them: they started loving them before they were pious.

Euthyphro doesn’t take up the second alternative, but it’s pretty easy to see why it’s unpalatable. Suppose the gods love pious things because they are all orange and that is the gods’ favorite color. This would not explain anything about piety; it’s just coincidental that pious things are orange. Or maybe the gods love pious things for reasons of their own that make no sense to us. Then we would not have much of an explanation of piety. That just says that it’s inexplicable.

The conclusion that Plato seems to have established is that even a supernatural being cannot make things right or wrong. That, according to Plato, has to established apart from whatever even the gods think or will.


The most obvious alternative to a theological origin for ethics is human culture. Glaucon introduces such a story and uses the story of the Ring of Gyges to highlight what he sees as its chief disadvantage: the system could not be sustained if people understood it this way. This leads the characters in the Republic to attempt to explain why justice is desirable for its own sake.

Louis related a different version of the Gyges story, from Herodotus. In this version, Gyges is a rather less willing participant in the whole affair. Interesting!

Key concepts

  1. The Euthyphro problem, that is, the problem with saying that things are good or bad because the gods decide that this is how it will be.
  2. Why the Ring of Gyges seems to raise problems for Glaucon’s story about the conventional origins of morality.
This page was written by Michael Green for Problems of Philosophy, Philosophy 1, Fall 2013. It was posted September 19, 2013.
Problems of Philosophy