Pope Francis's eco-encyclical, issued to great fanfare this week, might be hyperbolic, anti-progress, and seemingly keen to bring the hotness of hell up to Earth. (How else do we explain its mad aside against air-conditioning, which the pontiff brands as one of humanity's "harmful habits"? Clearly he wants to heat us up in preparation for our eternal frying for all the eco-sins we've committed.) But we should nonetheless be grateful that, for all its dottiness, this humanity-lecturing letter has been published. For it shows in black and white—and green—what a colossal amount in common there is between environmentalism and Catholicism. Environmentalism, writes Brendan O'Neill, rehabilitates in secular drag the stinging rebukes of humanity once delivered by pointy-hatted men of God.