Euthyphro: What is Piety?
The main theme of the argument being debated in Euthyphro is what constitutes piety. Socrates and the title character are both involved in lawsuits involving accusations of impiety. When Socrates pushes the Sophist to define the term, all he can do is provide examples. Ultimately, Socrates attacks the argument of his opponent that piety is reliant on instruction from the gods as to what is holy, but Socrates counters that such a definition merely means piety is what the gods say it to be. Under these conditions, if they had said the exactly opposite, then that would be considered pious behavior. Therefore, piety precedes the gods and what is holy exists outside religious tenets.
Apology: Personal Morality
The theme at work in the Apology has to do with doing that which is personally moral. If one is not willing to stand up for their beliefs in the face of harsh consequences—such as death—one can retain their moral worth even after death. If, on the other hand, one seeks the escape from responsibility of indulging in the pursuit of pleasures, the moral outrage will not only still remain unresolved, but they, t0o, will become morally and spiritually weaker.
Crito: The Just Response to Unjust Laws
The underlying theme of Crito has to do with what is just. In a society, laws are created by man with the result that inevitably some laws considered just by most will be considered unjust by some. This is unavoidable since due to the need to put the welfare of some people ahead of the interests of others. Because laws exist to foster a sense of order which in turn allows citizens to go about their business in a mental state not affected by chaos and fear, it is incumbent for every citizen to obey every law, even those they consider unjust even as they stand up to raise opposition to those the unjust nature of the law.
Phaedo: The Immortality of the Soul
The dialogue in Phaedo is a flashback to a discourse presided over by Socrates in his cell on the last day of his life. As a result, the nature of the discussion focuses on more metaphysical aspects than the others: the vastness of the universe and man’s small place within it and the case to be made for the existence of the soul and its ability to continue after the physical death of the body.