Editor’s Note: Each week we cross-post an excerpt from Katrina vanden Heuvel’s column at the WashingtonPost.com. Read the full text of Katrina’s column here.

Last month, Washington Post columnist Steve Pearlstein wrote that if you wanted to come up with a bumper sticker that defined the Republican Party’s platform it would be this: “Repeal the 20th century. Vote GOP.” With their unrelenting attempts to slash Social Security, end Medicare and Medicaid and destroy the social safety net, Republicans are, indeed, on a quest of reversal. But they have set their sights on an even bolder course than Pearlstein acknowledges in his column: It’s not just the twentieth century they have targeted for repeal; it’s the eighteenth and nineteenth too.

The eighteenth century was defined, in many ways, by the Enlightenment, a philosophical movement based on the idea that reason, rational discourse and the advancement of knowledge, were the critical pillars of modern life. The leaders of the movement inspired the thinking of Charles Darwin, Thomas Jefferson and Ben Franklin; its tenets can be found in the Declaration of Independence and the US Constitution. But more than 200 years later, those basic tenets—the very notion that facts and evidence matter—are being rejected, wholesale, by the twenty-first-century Republican Party.

The contempt with which the party views reason is staggering. Republicans have become proudly and unquestionably anti-science. (It is their litmus test, though they would probably reject the science behind litmus paper.) With the exception of Jon Huntsman, who polls about as well as Darwin would in a Republican primary, the Republican presidential candidates have either denied the existence of climate change, denied that it has been caused—and can be reversed—by man, or apologized for once holding a different view. They have come to this conclusion not because the science is inconclusive but because they believe, as a matter of principle, that scientific evidence is no evidence at all.

Editor’s Note: Read the full text of Katrina’s column here.