Modern Liberalism
The roots of Modern Liberalism (the form of Liberalism which we are familiar with) lie in the Progressive Era.
- First, in regard to science, today's liberals have a far more ambivalent attitude than the Progressives did. The latter had no doubt that science either had all the answers or was on the road to discovering them. Today, although the prestige of science remains great, it has been greatly diminished by the multicultural perspective that sees science as just another point of view.
- Second, liberalism today has become preoccupied with sex. Practices such as abortion and homosexual conduct -- the choice for which was recently equated by the Supreme Court with the right "to define one's own concept of existence, of meaning, of the universe, and of the mystery of human life" -- are considered fundamental rights.
- Third, contemporary liberals no longer believe in progress. The Progressives' faith in progress was rooted in their faith in science, as one can see especially in the European thinkers whom they admired, such as Hegel and Comte. When science is seen as just one perspective among many, then progress itself comes into question.
http://www.heritage.org/research/reports/2007/07/the-progressive-movement-and-the-transformation-of-american-politics