Within our collective grasp dwells the remarkable possibility of the abolition of biological aging. It's a big "if," but if we decide as a species to make this project a priority, there's around a 50% chance that practical rejuvenation therapies resulting in the comprehensive reversal of aging will be widely available as early as 2040. People everywhere, on the application of these treatments, will, if they wish, stop becoming biologically older. Instead, again if they wish, they'll start to become biologically younger, in both body and mind, as rejuvenation therapies take hold. In short,...