Socrates was a classical Greek philosopher whose thoughts had profound influence in his field. Little is known about his early and middle years, although according to ancient tradition, he worked as a stonecutter. The fact that he served as a heavily armed soldier in the Peloponnesian War indicates that during the early years of the war, he was roughly middle class, because men from this social class were required to provide their own armour. At some time during this period, Socrates began the mission of moral reform for which he became famous. He passed his time arguing about various moral subjects that interested him with his fellow Athenians and attempting to inspire them to be virtuous and honourable. Socrates' followers included not only Plato, but Alcibiades and Critias as well, both of whom later undermined the Athenian democracy. Possibly because of such notorious connections, Socrates was accused of impiety – showing a lack of respect for God – and corrupting youth. Different versions of the speech he made to defend himself against these accusations still exist today. In his speech, he described himself as a great benefactor to the city, and claimed that the Athenians would harm themselves in killing him. In spite of, or perhaps to some extent because of, his defence, Socrates was convicted, sentenced to death, and executed.