Euthyphro

Is based largely on "definition by division". Socrates goads Euthyphro to offer one definition after another for the word 'piety'. The hope is to use a clear definition as the basis for Euthyphro to teach Socrates the answer to the question, "What is piety?", ostensibly so that Socrates can use this to defend himself against the charge of impiety. It is clear that Socrates wants a definition of piety that will be universally true (i.e., a 'universal'), against which all actions can be measured to determine whether or not they are pious. It is equally clear that to be universal, the definition must express what is essential about the thing defined, and be in terms of genus, species, and its differentiae (this terminology is somewhat later than Socrates, made more famous with Aristotle). Hence this dialogue is important not just for theology, ethics, and epistemology, but even for metaphysics. Indeed: Plato's approach here has been accused of being too overtly anachronistic, since it is highly unlikely that Socrates himself was such a "master metaphysicist". But the more expository treatment of metaphysics we find in Aristotle has its roots in the Platonic dialogues, especially in the Euthyphro.