 Clever techniques of argument were taught by some sophists, as were serious devices for the effective staging of adversary debate, on which the city-states of those periods depended, both for decisions about policy and for verdicts in criminal cases. Some people felt that these techniques corrupted political and legal processes. Plato took pains to depict Socrates not only as different from the sophists, but as opposed to them on many points. This is a theme in several dialogues in our group: Euthydemus, Hippias Minor, Hippias Major, and Protagoras.