Horkheimer and Adorno, The Dialectic of Enlightenment “Enlightenment, understood in the widest sense as the advance of thought, has always aimed at liberating

Horkheimer and Adorno, The Dialectic of Enlightenment “Enlightenment, understood in the widest sense as the advance of thought, has always aimed at liberating human beings from fear and installing them as masters. Yet the wholly enlightened earth radiates under the sign of disaster triumphant” However it's a dense read; questioning rationality itself is somewhat broader than your specific question.