Es ist sehr interessant, daß die geschichtliche Periode, in der bei uns die Tradition des kritischen Denkens zum ersten Male einen entscheidenden Durchbruch erzielte, nämlich die Aufklärung, im deutschen Sprachbereich nur selten eine positive Würdigung erfährt. Man versieht sie gerne mit schmückenden Beiworten pejorativen Charakters wie „flach“, „unhistorisch“, „trocken“, bescheinigt ihr eine Überschätzung des bloß Vernünftigen und dokumentiert die eigene Überlegenheit damit, daß man bereit ist, dunklen, unklaren, widerspruchsvollen und vieldeutigen Ergebnissen geistiger Anstrengungen wegen ihrer angeblichen Tiefe den Vorzug vor den Resultaten klaren, nüchternen und kritischen Denkens zu geben.
Radiant with triumphant calamity
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 is radiant with triumphant calamity. Enlightenment’s program was the disenchantment of the world. It wanted to dispel myths, to overthrow fantasy with knowledge. Bacon, “the father of experimental philosophy,” brought these motifs together. He despised the exponents of tradition, who substituted belief for knowledge and were as unwilling to doubt as they were reckless in supplying answers. All this, he said, stood in the way of “the happy match between the mind of man and the nature of things,” with the result that humanity was unable to use its knowledge for the betterment of its condition. Such inventions as had been made—Bacon cites printing, artillery, and the compass—had been arrived at more by chance than by systematic enquiry into nature. Knowledge obtained through such enquiry would not only be exempt from the influence of wealth and power but would establish man as the master of nature. 
Encouraging an absolutist cast of mind
In their Dialectics of Enlightenment, the German philosophers Horkheimer and Adorno have argued that it was thus no accident that reason so often went hand-in-glove with ‘absolutism’. For reason and science, far from promoting liberty, encourage an absolutist cast of mind, by assuming an ‘absolute’ distinction between true and false, right and wrong, rather than a pluralist diversity of values. 
God: the ultimate guarantee for man’s freedom?
For instance, it was one thing for a circumscribed group of intellectuals to discuss atheism, as had happened up to now, quite another to arrange for its popular diffusion and propaganda via a publishing campaign like that attempted without great success by adherents of the Radical Enlightenment. It was one thing for the different Christian denominations and the great revealed religions to be split by bloody and incomprehensible theological controversies. It was another matter entirely to posit point blank the idea of establishing a new universal and natural religion common to all the peoples in the world, a religion that was rational—devoid of dogmas, churches, hierarchies, and priests—and that would take hold first among the élites and then among the rest of the population. This implied the existence of a God who was very far away and frankly uninterested in human events, and whose sole function was that of granting the ultimate guarantee for man’s freedom and responsibility and none whatsoever for the authority of any Church. [xii]
Enlightenment yet to be fully realised
Significantly, Adorno and Popper differed on the current state of the Enlightenment project. Whereas Adorno held that both totalitarian fascism and consumer capitalism have taken the Enlightenment to its self-destructive extreme, Popper held that the Enlightenment has yet to be fully realised. [148−9]
The price of knowledge
In his epistemological sensibility, Popper follows in the footsteps of the philosophers of the 18th-century Enlightenment. Their common starting point may be summarised in the following principle: The price of acquiring any knowledge at all is that it will be somehow distorted by the conditions of its acquisition; hence, criticism is the only universally reliable method.