Our concern for the future and our conception of human nature have both a philosophical dimension and a public policy dimension. Which would be the better way to spend our next dollar: on life-extension or on artificial intelligence? Manned space-exploration or robotic space-exploration? Answering such public-policy questions involves confronting some deep philosophical mysteries. If you were only concerned for your own survival, would you prefer to have your brain transplanted into another body, or have your brain scanned and its information realized in the hardware of a durable, Turing-testable robot? Would it be better to live one long life without offspring, or a short life leaving generations of descendants? If personal superlongevity and normal fertility would lead to overcrowding, which should we choose? Does considering "existential threats" change how we should answer? This article explores the conceptual and empirical interdependencies of these seemingly disjoint questions.