CLEVELAND — Cosmology used to be a heartless science, all about dark matter lost in mind-bending abysses and exploding stars. But whenever physicists and astronomers gather, the subject that roils lunch, coffee breaks or renegade cigarette breaks tends to be not dark matter or the fate of the universe. Rather it is about the role and meaning of life in the cosmos. Cosmologists held an unusual debate on the question during a recent conference, "The Future of Cosmology," at Case Western Reserve University here. According to a controversial notion known as the anthropic principle, certain otherwise baffling features of the...