Socrates (shown here in a copy of a bust originally attributed to the Greek sculptor Lysippus) was a Greek philosopher and teacher who lived in Athens, Greece, in the 400s bc. He profoundly altered Western philosophical thought through his influence on his most famous pupil, Plato, who passed on Socrates’s teachings in his writings known as dialogues. Socrates taught that every person has full knowledge of ultimate truth contained within the soul and needs only to be spurred to conscious reflection in order to become aware of it. His criticism of injustice in Athenian society led to his prosecution and a death sentence for allegedly corrupting the youth of Athens.