There is an argument near the beginning of Euthyphro that Socrates tries to make to Euthyphro in which I believe that Socrates makes a logical mistake. It's a pretty basic mistake, so rather than assume that Plato made such a simple error, I'd like to ask everyone here what they think. All quotations are taken from G. M. A. Grube's translation of Euthyphro in Plato's Complete Works, edited by John M. Cooper.
In 7b-d, Socrates says:
"What are the subjects of difference that cause hatred and anger? ...What subject of difference would make us angry and hostile to each other if we were unable to come to a decision? Perhaps you do not have an answer ready, but examine as I tell you whether these subjects are the just and the unjust, the beautiful and the ugly, the good and the bad. Are these not the subjects of difference which, when we are unable to come to a satisfactory decision, you and I and other men become hostile to each other whenever we do?"
Now, if we let D be the statement, "We disagree about goodness, justice and beauty" and let H be the statement "We become hostile to/at odds with each other," Socrates seems to be saying here that D causes H.
I interpret D causes H to mean if D, then H.
Then, in 7e, Socrates goes on to say:
"Then according to your argument, my good Euthyphro, different gods consider different things to be just, beautiful, ugly, good, and bad, for they would not be at odds with one another unless they differed about these subjects, would they?" (Emphasis mine)
This statement, I interpret to mean not H, unless D, which is the same as if not D, then not H, which, by contraposition, is equivalent to if H, then D.
The first and second quotations here thus lead to the following two statements, respectively:
1) if D, then H
2) if H, then D
But 1) does not entail 2)! Nor does 2) entail 1), for that matter. They are converses of each other. So how can Socrates make the claim in 7e that 1), which was established earlier, entails 2)? Clearly, 1) does not entail 2).
This seems like a straightforward error to me, but I don't feel comfortable accusing Plato of such a basic mistake. Perhaps I am misreading or misinterpreting something here? What does everyone else think?