The main metaphor employed by Socrates in Crito comes toward the beginning of the dialogue. In efforts to explain to his companion, Crito, the reasoning behind his decision to ignore public sentiment and escape, Socrates likens himself to a medical patient. He asserts that if he had an illness, he would not heed the advice of his friends, who had no medical knowledge, but would instead do whatever the doctor recommended.

Socrates elaborates, "So he ought to regulate his actions and exercises and eating and drinking by the judgment of his instructor, who has expert knowledge, rather than by the opinions of the rest of the public."

This method helps Socrates open Crito's mind to instructive discourse, which eventually proves Socrates' logic over Crito's.