Socrates was one of the most famous Greek philosophers whose teaching Plato reported in his dialogues.
Public Domain. Courtesy of Wikipedia.
Socrates
Socrates (c. 470–399 B.C.), who was also a soldier during the Peloponnesian War and a stonemason after, was renowned as a philosopher and educator. In the end, he was accused of corrupting Athens' youth and for impiety, for which reasons he was executed in the Greek manner -- by drinking poisonous hemlock.