why Socrates took the cup of poisonor the cup of eternal sleep?

On a day in 399 BC the philosopher Socrates stood before a jury of 500 of his fellow Athenians accused of "refusing to recognize the gods recognized by the state" and "of corrupting the youth." If found guilty; his penalty could be death. The trial took place in the heart of the city, the jurors seated on wooden benches surrounded by a crowd of spectators. Socrates' accusers (three Athenian citizens) were allotted three hours to present their case, after which, the philosopher would have three hours to defend himself.

Socrates was 70 years old and familiar to most Athenians. His anti-democratic views had turned many in the city against him. Two of his students, Alcibiades and Critias, had twice briefly overthrown the democratic government of the city, instituting a reign of terror in which thousands of citizens were deprived of their property and either banished from the city or executed.

After hearing the arguments of both Socrates and his accusers, the jury was asked to vote on his guilt. Under Athenian law the jurors did not deliberate the point. Instead, each juror registered his judgment by placing a small disk into an urn marked either "guilty" or "not guilty." Socrates was found guilty by a vote of 280 to 220.

The jurors were next asked to determine Socrates' penalty. His accusers argued for the death penalty. Socrates was given the opportunity to suggest his own punishment and could probably have avoided death by recommending exile. Instead, the philosopher initially offered the sarcastic recommendation that he be rewarded for his actions. When pressed for a realistic punishment, he proposed that he be fined a modest sum of money. Faced with the two choices, the jury selected death for Socrates.

The philosopher was taken to the near-by jail where his sentence would be carried out. Athenian law prescribed death by drinking a cup of poison hemlock. Socrates would be his own executioner.

It was better than the alternative (stoning).