On a March day in the year 399 BC, a 70-year-old man stands trial in Athens, a man well known in the city as a familiar figure. Even his appearance makes him a curiosity: he looks like a forest sprite and walks around in the same threadbare cloak summer and winter. He mostly spends his time in the Agora in the centre of the city, surrounded by a large crowd of young people, almost all of whom come from the most respected Attic families. The teenagers join in with enthusiasm and curiosity when the old man pursues his favourite pastime and questions locals and strangers alike, especially the politicians and scholars among them, to find out whether they possess real knowledge. The outcome of this examination usually turns out painfully for the person questioned.
Although he exposes every one of his conversation partners for their ignorance, the questioner astonishingly claims about himself that he knows that he knows nothing.