1:

Each society has its regime of truth, its ‘general politics’ of truth: that is, the types of discourse that it accepts and makes function as true; the mechanisms and instances which enable one to distinguish true and false statements, the means by which each is sanctioned; the techniques and procedures accorded value in the acquisition of truth; the status of those who are charged with saying what counts as true.

Michel Foucault, Power/Knowledge, 1980.

2:

Truth for [Foucault] is not something absolute that everyone must acknowledge but merely what counts as true within a particular discourse… However, it is not difficult to show that a relativist concept of truth of this kind is untenable. If what is true is always relative to a particular society, there are no propositions that can be true across all societies. However, this means that Foucault’s own claim cannot be true for all societies. So he contradicts himself. What he says cannot be true at all.

The relativist fallacy also applies to the concept of knowledge. One cannot hold that there are alternative, indeed competing, forms of knowledge, as Foucault maintains. Inherent in the concept of knowledge is that of truth. One can only know something if it is true. If something is not true, or even if its truth status is uncertain, one cannot know it. To talk, as Foucault does, of opposing knowledges is to hold that there is one set of truths that runs counter to another set of truths. It is certainly possible to talk about beliefs or values that may be held in opposition by the authorities and by their subjects, since neither beliefs nor values necessarily entail truth. But Foucault’s idea that there are knowledges held by the centralising powers that are opposed to the subjugated knowledges of the oppressed is an abuse of both logic and language.

Keith Windschuttle, The Killing of History: How Literary Critics and Social Theorists are Murdering Our Past, 1996.

3:

foucault, n. A howler, an insane mistake. “I’m afraid I’ve committed an egregious foucault.”

From the Philosophical Lexicon.