Ostensibly in order to better defend himself in an upcoming trial for being an impious citizen of Athens, Socrates asks Euthyphro for a clear definition of piety (holiness); he offers Socrates four definitions.
First definition
Euthyphro's first definition of piety is what he is doing now, that is, prosecuting his father for manslaughter (5d). Socrates rejects Euthyphro's definition, because it is not a definition of piety, and is only an example of piety, and does not provide the essential characteristic that makes pious actions pious.
Second definition
Euthyphro's second definition: Piety is what is pleasing to the gods. (6e–7a) Socrates applauds this definition, because it is expressed in a general form, but criticizes it saying that the gods disagree among themselves as to what is pleasing. This means that a given action, disputed by the gods, would be both pious and impious at the same time – a logical impossibility. Euthyphro argues against Socrates' criticism, by noting that not even the gods would disagree, among themselves, that someone who kills without justification should be punished. Yet Socrates argues that disputes would still arise – over just how much justification actually existed; hence, the same action could be pious and impious; again, Euthyphro's definition cannot be a definition of "piety".
Third definition
To overcome Socrates' objection to his second definition of piety, Euthyphro amends his definition. (9e)
Euthyphro's third definition of piety is: "What all the gods love is pious, and what they all hate is impious." In reply, Socrates poses the question that would eventually become known in philosophy as the Euthyphro dilemma: "Is the pious loved by the gods because it is pious? Or is it pious because it is loved by the gods?". Euthyphro seems unsure as to what the question means and so Socrates applies a dialectic technique: an analogy, to clarify his question (10a). He persuades Euthyphro to agree that when we call a thing "carried", it is simply because it is being carried by someone and not because it possesses an inherent characteristic, which could be called "carried". That is, "being carried" is not an essential trait of the thing being carried but a condition, a state that the object is currently in. He then moves to what we call "beloved" (φιλούμενόν filoumenon). Is something "beloved" in and of itself (like being big or red), or does it become beloved when it is loved by someone? Clearly, the answer is again the latter, something becomes beloved when it is loved. So then, continues Socrates, something beloved by the gods (θεοφιλές theofiles) becomes so because it is loved by them, to which Euthyphro agrees and Socrates moves to the conclusion that reveals his contradiction: What is beloved by the gods cannot be pious. Euthyphro seems to be taken aback so Socrates reminds him the definitions he gave previously (10e). He had said that something is loved by the gods because it is pious, which means that their love follows from something inherent in the pious. And yet they just agreed that what is beloved is put in that state as a result of being loved. So piety cannot belong to what is beloved by the gods since according to Euthyphro it does not acquire its characteristics by something (the act of being loved) but has them a priori, in contrast to the things that are beloved that are put in this state through the very act of being loved. It seems therefore that Euthyphro's third argument is flawed.
At that juncture of their dialogue, Euthyphro does not understand what makes his definition of "piety" a circular argument; he agrees with Socrates that the gods like an action because it is pious. Socrates then argues that the unanimous approval of the gods is merely an attribute of "piety", that divine approval is not a defining characteristic of "piety". That divine approval does not define the essence of "piety", does not define what is "piety", does not give an idea of "piety"; therefore, divine approval is not a universal definition of "piety".
- Linguistic note
Socrates' argument is convoluted not only because of its structure but because of the language used, and is said to have "reduced translators to babble and driven commentators to despair".[6] The text presents the argument through a distinction between the active and the passive voice, as for example when Socrates asks about the difference between a "carried thing" (φερόμενον) and "being carried" (φέρεται), both using the word "carried" in the English translation.
Fourth definition
In the second half of the dialogue, Socrates suggests a definition of "piety", which is that "piety is a part of justice",[7] but he leads up to that definition with some other observations and questions, starting with:
... Are you not compelled to think that all that is pious is just?
Yet, Socrates later says that the information provided in his question to Euthyphro is insufficient for a clear definition of "piety", because piety belongs to those actions we call just, that is, morally good; however, there are actions, other than pious actions, which we call just (12d); for example, bravery and concern for others. Piety is only a portion of Justice and is not sufficient in giving a clear view of justice. Socrates gives a comparison to even numbers. If a definition of even numbers were provided it would not be suitable to clarify what numbers are because it is only a group of numbers and not the entire thing as a whole. Socrates asks: What is it that makes piety different from other actions that we call just? We cannot say something is true, because we believe it to be true. We must find proof.
Euthyphro's response
In response, Euthyphro says that piety is concerned with looking after the gods (12e), but Socrates objects, saying that "looking after", if used in its ordinary sense (with which Euthyphro agrees) would imply that when one performs an act of piety one thus makes one of the gods better – an example of hubris, a dangerous human emotion frowned upon by the Greek gods. (13c) In turn, Euthyphro responds that "looking after" involves service to others, and Socrates asks: What is the end product of piety? Euthyphro replies with his earlier (third) definition, that: Piety is what is loved by all the gods. (14b).
Final definition
Euthyphro then proposes a fifth definition: "Piety is an art of sacrifice and prayer". He proposes the notion of piety as a form of knowledge, of how to do exchange: Giving gifts to the gods, and asking favours in return. (14e) Socrates presses Euthyphro to say what benefit the gods perceive from human gifts – warning him that "knowledge of exchange" is a type of commerce. (14e) Euthyphro objects that the gifts are not a quid pro quo, between man and deity, but are gifts of "honour, esteem, and favour", from man to deity. (15a) In other words, Euthyphro admits that piety is intimately bound to the likes of the gods. The dialogue has come full circle, and Euthyphro leaves Socrates without a clear definition of "piety" as he faces a trial for impiety (ἀσέβεια asebeia).
