Asks Paul Craig Roberts.

His answer:

I once offered this explanation:

The liberals’ stress on social purification flows from an inconsistency in the intellectual foundation of Western civilization.  The Enlightenment had two results that combined to produce a destructive formula.  On the one hand, Christian moral fervor was secularized, which produced demands for the moral perfection of society.  On the other hand, modern science hammered epistemology into a critical philosophical positivism that is skeptical of the reality of moral motives.  From the one we get moral indignation and from the other, moral skepticism.  How can two such disparate tendencies be reconciled?

The answer seems to be that this inconsistent combination is held together by their joint attack on existing society.  One pre-empts existing society’s defense, while the other focuses moral indignation against it.  Together, they support a social and political dynamism that seeks to achieve progress by remaking society.

Affirmations of society’s achievements run into this dynamism, which mows them down with skepticism and indignation.  People who are motivated by moral purposes  find that they have a safe outlet only in accusations of immorality against existing society, and the West’s morality becomes immanent in attacks on itself.

Others, such as Richard Knight, believe Western civilization was destroyed by German Jewish cultural marxists whose march through the institutions discredited every institution of Western civilization. I don’t disagree that this has occurred, but I think Cultural Marxism is itself a product of the inconsistency in the Western intellectual foundation that I described. 

It seems unlikely that the West’s intellectuals can escape the destructive dynamism of moral indignation and moral skepticism.  When civilization is destroyed, nirvana is not standing ready to take its place.  The replacement is barbarism into which we are already descending.