"They are men and women who tend to believe that the human being is perfectible and social progress predictable, and that the instrument for effecting the two is reason; that truths are transitory and empirically determined; that equality is desirable and attainable through the action of state power; that social and individual differences, if they are not rational, are objectionable, and should be scientifically eliminated; that all people and societies strive to organize themselves upon a rationalist and scientific paradigm." -- William F. Buckley
Once again, Mr. Conservatism's penetrating wit encapsulates the many fallacies of liberalism.
At length, here are the extended arguments for his precise assertions"
The main bias of liberalism is the primacy and supremacy of reason.
Free market economist Friedrich Hayek slayed this naive notion with "The Fatal Conceit," demonstrating with logic, reason, history, and custom that the means and methods of this life did not emerge by human planning or speculation, but by trial and error, tradition operating between instinct and ingenuity.
Those practices conductive to life thrives, those which failed to promote trade, wholeness, and general welfare, died out along with those peoples who attempted to live by them.
Regarding the perfectibility of man, no one can speak enough against the shallow, foolish, and dangerous notion that human beings can one day achieve a state of perfection. The Nazi regime sprang forth in part from this heinous notion, which in turn justified prejudice, segregation, and ethnic cleansing en masse. The Triumph of Reason became the Defeat of Rationalism, a mode of thinking so debilitating and self-limiting that any society convinced of its own genius must necessarily succumb and perish.
The morals of our behavior cannot be dictated or determined by our reason. "No 'is' implies and 'ought'" David Hume was not acquiescing to relativistic cynicism in divorcing the assailable assumption that we can reason out right and wrong on our own; rather, he was championing the historical truth that right and wrong as civilized categories must be reasoned out in accordance with culture, history, and practice. The intellect unaided gives birth to inscrutable tyrannies antithetical to real life.
Real life, by the way, is premium which the mind can appreciate, but not create or replicate. A matter of faith and tradition operating with individual experimentation, the processes and practices which do work (as opposed to those which "should work") surpass any solipsistic notion of what makes sense to the limited human intellect. Planned societies are destined to fail, just as centralized economies waste and waste away with every attempt to constrain the means and motivations of industry.