The phrase is French -- La Trahison des clercs”, meaning roughly the treason of the intellectuals. This particular phrase, launched by Julien Benda in 1927, could only have popped out of a French head. Benda’s beef was that the intellectuals of his day were placing the virtue of action above the necessity of lucid thinking. Opinion makers, Benda feared, were allowing political commitment to strangle thought. As Roger Kimball put it in a 1992 essay in the New Criterion, "Benda claimed, politics was THE ideal of disinterestedness, the universality of truth: such guiding principles were contemptuously deployed as masks when they were not jettisoned altogether. It was in this sense that he castigated the 'desire to abase the values of knowledge before the values of action.'”
When intellectuals abandon “the universality of truth” for political reasons, they are guilty of intellectual treason. During Benda’s own day, politicians were wearing convincing but false masks of intellectualism; think of Stalin in Russia, Hitler in Germany, Mussolini in Italy, and the choir of intellectuals who surrounded them. Suitably abased, knowledge yielded to political force blind to truth.