Watch "The Tau Manifesto" speech by Hartl where he, in great detail, explains the arguments for tau being a more natural constant number than pi. As a "truth-seeker" he cares about the correctness of explanation and as a teacher, he cares about clarity in math. He admits topping pi with tau could be a hefty task, though. "We are up against a powerful enemy," he says. "There is a centuries-old conspiracy to propagate pro-pi propaganda."