's dominating concept is that of truth
, that the thing accepted as truth is most definitely not Truth (TM). That is, what we believe to be truth is not the key to the universe
, but rather something more temporary, a truth that changes depending on who has the power
to force its acceptance.
Indeed, we see this in science in numerous cases. As noted in "Coming to Blows...", Copernicus faced incredible opposition in advocating the heliocentric view of the universe. Before this, Galileo faced the same opposition, only with much greater consequences. In more modern times Albert Einstein's Theory of Relativity rocked the scientific world in it's novelty. He was lucky enough to have scientific proof on his side to overcome the overwhelming power of intellectual stagnation.
This is effectively the same argument adopted by Thomas Kuhn. He postulates that major change in belief does not occur unless it is convenient to believe in it. This is a more general explanation than offered by Foucault, actually, a superset. While Foucault talks about truth in terms of a person wielding power, Kuhn abstracts the person with power into a matter of convenience, though he does not mention to whom it is convenient.
Edward Rothstein notes(1), for example, the medieval notions of body humours and phlogiston controlling certain aspects of the body. These ideas were discarded not because they were disproven, but rather because another set of ideas was more convenient to believe(1). This is prima facie evidence that the new beliefs and likely, the old ones too are invalid. While we might wish it not to be so, to Kuhn and Foucault both, searching for truth does not happen for love of the truth, but rather for personal gains of those doing the searching.
(1) "Coming to Blows Over How Valid Science Really Is", Edward Rothstein, New York Times, 21 July 2001