Note: There are no natural breaks in the text as Plato wrote it. These notes on the text have been divided artificially, sections beginning or breaking off where a new theme or topic is introduced or dropped. Because page numbers may vary from edition to edition, these sections have been demarcated according to the Stephanus numbers, the page numbers from the 1578 complete works edited by Henri Estienne ("Stephanus" in Latin). The Stephanus numbers are the standard page references in scholarly work on Plato, and most editions of his work contain the Stephanus numbers along the margins.
Socrates and Euthyphro meet by the Porch of the King Archon, one of the judges responsible for overseeing religious law. Euthyphro, surprised to see Socrates, asks what brings him here. Socrates answers that he is being prosecuted by Meletus--a young unknown with straight hair, a sparse beard, and a hooked nose. Meletus believes Socrates is corrupting the youth of Athens, and wants to prosecute him. Socrates remarks what a promising young start this Meletus is making, weeding out the corruptors of the city's youth: Socrates himself believes that the excellence of the youth should be of utmost concern. Meletus has also accused Socrates of inventing new gods and not recognizing those that exist.
Euthyphro remarks that this accusation is probably connected to the divine sign that Socrates claims to be visited by on occasion. Euthyphro, too, is often disbelieved when he speaks about divine matters or predicts the future. He reassures Socrates that one must simply endure these prejudices, and asserts his confidence that Socrates will come out fine in the end.
Socrates inquires as to why Euthyphro has come to court, and Euthyphro answers that he is prosecuting his father for murder (which was considered a religious crime by the Greeks). Socrates is amazed that Euthyphro should want to prosecute his own father, remarking that Euthyphro must have very advanced knowledge of these sorts of matters to be making such a bold move. And, Socrates suggests, his father must have killed another family member: surely, Euthyphro would not go to such pains on behalf of an outsider.
Euthyphro replies that he is indeed an expert in these matters, and that, contrary to Socrates' suggestion, the murdered man is not of Euthyphro's family. All that matters in these cases, Euthyphro asserts, is whether or not the killer killed with justification: we should make no exceptions even if the murderer is our father and the murdered man is not close to us. His father has committed an impious act that pollutes Euthyphro and his whole family, and this sin must be purged by means of prosecution.
It turns out that the murdered man was a hired hand of Euthyphro's, helping with the farming on Naxos. The man got drunk and, in a rage, slit the throat of one of Euthyphro's servants. Euthyphro's father bound this murderer, threw him in a ditch, and sent for the Interpreter, the official who is responsible for dealing with such crimes. But before the Interpreter could arrive, the hired hand died of exposure in the ditch. Euthyphro notes that his family is angry with him for carrying out such a prosecution on behalf of a murderer, but Euthyphro asserts that he knows better than they do the position of divine law regarding what is holy and what is unholy.
Socrates is treating Euthyphro as the teacher when in fact Socrates is teaching Euthyphro
Plato suggesting that there is no such thing as a definition of holiness, that there is no one feature that all holy deeds have in common?
What Plato/Socrates is challenging is Euthyphro's/everyone's knowledge or assumed knowledge of anything, not the can we know anything idea, but have we challenged our beliefs? Are we sure that the conclusion we hold is conclusion enough? Peirce and James pick this up again a few years later.