Why did the Athenians put Socrates to death?

For two charges, being:

Asebeia (impiety) against the pantheon of Athens, and corruption of the youth of the city-state.

In 399BC, Socrates was sentenced to death. The charges, as far as we can reconstruct them, were vague: impiety, worshipping new gods, corrupting the young. It is startling that such accusations led to a death sentence: Athens was a radical democracy that prided itself on freedom of speech, and all that Socrates did was talk.

In his new book, Robin Waterfield sets out to explain why Socrates died: he discusses his trial, but also offers an informed and well-written account of classical Athenian history. He starts by describing accurately, and in vivid detail, how the courts worked, how prosecution and defence speeches were timed, and how a massive jury voted - immediately after hearing the speeches - on the guilt or innocence of the defendant. In Socrates' case, the jury convicted him by a narrow majority. To understand that instantaneous verdict, Waterfield then offers a readable and interesting account of Athenian history in the decades preceding the trial.

In the late 5th century BC, Athens waged a long, exhausting war against Sparta, which ended in defeat. Meanwhile, a typhoid epidemic killed at least 25 per cent of the population. And then there were two brutal oligarchic coups: the first in 411BC, the second in 404BC. The democracy was finally restored in 403-02BC, but society had changed.

Waterfield describes well the ambitious and unscrupulous characters that dominated the public life of the age. There was Alcibiades, famous for his looks, his horses, his wealth and his drunken excesses: he was a prominent Athenian general who defected to Sparta, then to Persia and finally plotted against the democracy in 411BC.

And there was Critias, one of the 30 tyrants who seized power in 404BC: while he was in power, hundreds of Athenians were sentenced to death by drinking hemlock, and many more were forced into exile.

Socrates had a tumultuous on-off love affair with Alcibiades for several years, and also taught Critias. Waterfield argues that he died because of his erotic and pedagogical association with the most violent and outrageous anti-democrats of his time.

By 399BC, Critias and Alcibiades had both been killed - but Socrates, according to Waterfield, was unfinished business. There is no doubt that Socrates' flirtations with flamboyant aristocrats such as Alcibiades counted against him in court. This is not just Waterfield's theory: it is a view that circulated in ancient Athens, too.

But to understand why Socrates died, it is important to consider other factors, not least Socrates' own behaviour. Plato suggests that Socrates engineered his own death, and there is doubtless some truth to that.

Technically, his trial fell under the category of "assessed trials", in which the state acknowledged that there could be different degrees of guilt. If the defendant was found guilty, the prosecutor would propose a penalty and the defendant would propose a lesser counter-penalty; and there was then a second round of voting. Socrates made a mockery of the whole procedure: rather than proposing a fine or exile, he insisted that he wanted "free dinners at public expense". After he died, nobody quite knew how it could have happened.

Plato and Xenophon tried hard to explain it, and we know that dozens of others wrote about Socrates, as hundreds of pamphlets about him circulated soon after his death. And then there were those who, in true Socratic fashion, refused to write, but preached in the streets instead.