Al Gore gave a speech last week “challenging” America to run “on 100% zero-carbon electricity in 10 years”—though that’s just the first step on his road to “ending our reliance on carbon-based fuels.” Serious people understand this is absurd. Maybe other people will start drawing the same conclusion about the man proposing it. ... A more interesting question is why Mr. Gore remains believable. Perhaps people think that facts ought not to count against a man whose task is to raise our sights, or play Cassandra to unbelieving mortals. Or maybe he is believed simply because people want something in which to believe. “The readiness for self-sacrifice,” wrote Eric Hoffer in “The True Believer,” “is contingent on an imperviousness to the realities of life. . . . All active mass movements strive, therefore, to interpose a fact-proof screen between the faithful and the realities of the world. They do this by claiming that the ultimate and absolute truth is already embodied in their doctrine and that there is no truth nor certitude outside it. . . . To rely on the evidence of the senses and of reason is heresy and treason. It is startling to realize how much unbelief is necessary to make belief possible.”