A famous formula, the Drake Equation (explained here), argues there must be life elsewhere in the universe, based on probability principles. But Columbia University Professor David Kipping (profiled here) says, “Not so fast.” The devil is in the details. The moral of his 26-minute lecture (watch video) is we don’t know; and when you don’t know, it’s okay to be agnostic about it and not express a belief one way or the other. That can apply to lots of things.