As was mentioned earlier, one great source of these prejudices against Socrates comes from Aristophanes' The Clouds, in which Socrates is portrayed as an eccentric old fool who floats about suspended from a crane, spouting all sorts of nonsense about the heavens and the earth. Aristophanes also characterizes Socrates as charging a fee for his services. The Clouds was written in 423 B.C., 24 years before this trial, so whether it is the source of these prejudices or a reflection of even older prejudices, we can see that accusations against Socrates date from long before the trial.
Socrates' confession that he lacks any kind of expertise in any field whatsoever is central to his philosophy, and sets him apart from both the sophists and the Presocratics. Teachers from these two groups both claimed that through experience, inspiration, or investigation, they had gained access to special knowledge that could be taught. Socrates, on the other hand, never makes any particular claims to knowledge, and his inquiries tend to show the ignorance of his interlocutors rather than his own expertise. Socrates, then, has no particular knowledge, as such, to teach at all, but has instead a peculiar kind of wisdom that will be clarified in the sections following.