The paper deals with Foucault’s last lectures at the Collège de France (1981 – 1984). Their main theme is relationship between subject and truth. In the Hermeneutics of the subject, Foucault starts to study a concept of the care of the self which has acquired an ethical dimension in Socrates, and wants to follow its transformations into later Greek-Roman philosophy. On the basis of three texts by Plato, he shows that the Socratic-Platonic concept of self-concern is closely connected with self-knowledge. In his last lecture entitled The courage of the truth, Foucault compares it with a Cynical approach to life. Now, he can see that there is a difference between Socrates and Diogenes that gives the Cynical way of life a different character. This difference plays an important role in the history of Western subjectivity.