... "Do you now tell me likewise in regard to life and death. Do you not say that death is the contrary of life?"
"I say so."
"And that they are produced from each other?"
"Yes."
"What then is that which is produced from life?"
"Death," said Cebes.
"And that which is produced from death?"
"I must allow," said Cebes, "to be life."
"Therefore, our souls exist after death."
This is one formal argument of Socrates.