Having claimed that he is not like either the Presocratics or the sophists, Socrates opens himself up to the question of what might have led to these false accusations. He answers that he has developed a reputation for wisdom--but a kind of limited, human wisdom, not the kind of super-human wisdom that would be required to speak authoritatively about matters such as the Presocratics and the sophists discuss. This reputation originated in a prophecy given by the oracle at Delphi to his friend Chaerephon. Chaerephon asked the omniscient oracle if there was anyone wiser than Socrates, and the priestess replied that there was not.
Socrates recounts how he took this news with great puzzlement: he knew the oracle could not lie, and yet he was only too aware that he had no particular wisdom or specialized knowledge at all. In order to test the oracle, or to prove it wrong, Socrates sought out and questioned Athenian men who were highly esteemed for wisdom. First, he interrogated the politicians, then the poets, and then the skilled craftsmen. In questioning the politicians, he found that though they thought they were very wise, they did not in fact know much of anything at all. The poets, though they wrote great works of genius, seemed incapable of explaining them, and Socrates concluded that their genius came not from wisdom but from some sort of instinct or inspiration which was in no way connected to their intellect. Furthermore, these poets seemed to think they could speak intelligently about all sorts of matters concerning which they were quite ignorant. In the craftsmen, Socrates found men who truly did have great wisdom in their craft, but invariably, they seemed to think that their expertise in one field allowed them to speak authoritatively in many other fields, about which they knew nothing. In each case, Socrates affirmed that he would rather be as he is, knowing that he knows nothing, than to be inflated by a false sense of his own great wisdom. Thus, he concludes, he truly is wiser than other men because he does not think he knows what he does not know.
Though many bystanders take Socrates to be an expert in the fields in which he questions others, Socrates denies any expertise, and interprets the oracle as saying that the wisest of men are men like Socrates who humbly accept that their wisdom is deficient. He feels it his duty to the God of the oracle to continue questioning men who think they are wise in order to show them that they are not. The result has been to earn him many young admirers, and to earn the deep resentment of those whose ignorance he makes evident. These men lack any substantial reason for disliking Socrates, and so, Socrates claims, they invent charges against him, accusing him of being a sophist or a Presocratic. This they prefer to accepting the truth: that they are far more pretentious than they are wise.
The oracle of Apollo at Delphi was the most famous and most revered oracle of the ancient world. That Chaerephon did in fact visit the oracle is confirmed by Xenophon, though in his account, the oracle declared Socrates to be "the most free, upright, and prudent of all people" (Xenophon, Socrates' Defense) rather than the most wise. In either case, it is clear that the oracle made a positive claim about Socrates. Most of Plato's early dialogues--those that center more on Socrates' thought than on Plato's own--are concerned with ethical questions, and so we can perhaps reconcile Xenophon's and Plato's accounts by saying that Socrates' wisdom is a kind of ethical wisdom, one that would make him supremely free, upright, and prudent. But the Delphic oracle sided primarily with Sparta during the Peloponnesian War, so it is doubtful how much an Athenian jury would trust or appreciate the evidence given by the oracle.
Also of relevance is the famous motto inscribed above the entrance to the oracle at Delphi: "Know thyself." Socrates is an ardent advocate of self- knowledge, and his investigations can be seen as an attempt to come to a better understanding of his own nature. He is famous for claiming that no one could ever knowingly and willingly do evil, that evil is a result of ignorance and deficient self- knowledge. His investigations generally ask such questions as what it is to be virtuous, or pious, or just. In his dogged efforts to understand these terms himself, and his persistence in showing his interlocutors to be wrong in assuming they have such understanding, Socrates reveals himself as a man intent on gaining the self-knowledge necessary to lead a virtuous life.
Socrates' account of his conversations with the supposed wise men of Athens provides us with a valuable account of his method of elenchus, or cross-examination. The Apology is a rare exception in Plato's works, in that only a small part of it is given over to the elenchus; in most of the works, it is the principal means by which Plato lays out Socrates' arguments. The elenchus begins with Socrates' interlocuter claiming to have a perfect understanding of some term, usually an ethical term like "justice," "virtue," or "piety," though epistemology and metaphysics are sometimes discussed in Plato's more mature work. Socrates then proceeds to question his interlocutor about his knowledge of that term, trying to arrive at the essence of the matter. Usually, the interlocutor will manage to find several cases that he thinks exemplify that term, but he will have trouble saying what they all have in common that make the given term apply to them. Through careful interrogation, Socrates will show that his interlocutor does not in fact know anything more than a few scattered and imprecise examples.