Michel Foucault, "Truth and Power"

The important thing here, I believe, is that truth isn't outside power, or lacking in power: contrary to a myth whose history and function would repay further study, truth isn't the reward of free spirits, the child of protracted solitude, nor the privilege of those who have succeeded in liberating themselves. Truth is a thing of this world: it is produced only by virtue of multiple forms of constraint. And it induces regular effects of power. Each society has its régime of truth, its 'general politics' of truth: that is, the types of discourse which it accepts and makes function as true [...]

The problem is not changing people's consciousness - or what's in their heads - but the political economic, institutional régime of the production of truth.

It's not a matter of emancipating truth from every system of power (which would be a chimera, for truth is already power) but of detaching the power of truth from the forms of hegemony, social, economic and cultural, within which it operates at the present time.

The political question, to sum up, is not error, illusion, alienated consciousness or ideology; it is truth itself.

Power/Knowledge (New York: Pantheon Books, 1980), 131-3.