John Gray:

Evangelical Christians will look at you with blank disbelief if you suggest that Christian teachings played any part in the Inquisition, the early modern witch craze or later forms of persecution. “How could a religion of love,” they splutter, “possibly be responsible for such hateful crimes?” Similarly, today’s Enlightenment evangelists respond to the fact that some of the worst modern crimes have been committed by militant secular regimes with incredulity: “How could a philosophy of reason and humanity possibly be involved in anything so irrational and inhuman?”

These responses illustrate one of the central tenets of fundamentalism: the pristine creed is innocent of all evil. Any fact that runs counter to this conviction is screened out by what Karl Popper – one of the more interesting 20th-century Enlightenment thinkers, who along with Freud is absent from Pagden’s account – called a strategy of immunisation. Just as any Christian who participated in hate crimes can’t really be a Christian, anyone who took part in bloodthirsty political experiments such as Jacobinism and communism can’t really belong in the Enlightenment.

To departisanize a favorite saying of a partisan hack blogger, ideologies can never fail, they can only be failed.