These lectures, delivered by Foucault at the Collège de France in 1982 and 1983, meditate on the concept of truth-telling known as parresia. The bulk of these lectures have Foucault tracing the use, exercise, and implications of parresia through ancient Greek texts.
Foucault starts, however, in the Enlightenment.

In his reflections on the Enlightenment, Kant speculated that the human race was making progress. He figured that popular support abroad for the ideals propelling the French Revolution symbolized this progress. Man was leaving an era in which he was unwilling to use his reason. Now, he would reason; and, once free to exercise his reason, he could be obedient. More freedom of thought, more obedience. And this obedience requires a kind of self-governance that Foucault interrogates in much of his work.
After a brief visit with the Enlightenment, Foucault starts to dwell in the ancient texts, starting with the myth of Ion and rounding the final corner with Plato's Phaedrus. In these stories he identifies the roles and implications of courage, politics, rhetoric, and philsosophy in the practice and concept of truth-telling known as parresia.
To my mind, this was so far the least compelling of these newly published Foucault lectures. But my mind is somewhere else now, maybe.
Notes:
* Prior to the Enlightenment, people spoke of the present in terms of periods of prosperity or decadence.