The philosopher Thomas Nagel’s new book, “Mind and Cosmos: Why the Materialist Neo-Darwinian Conception of Nature Is Almost Certainly False,” restores the primal force of a great old philosophical word, “metaphysics.” He starts with a boldly discerning look at that strange creature, mankind, and comes to some remarkable speculations about who we are and what our place is in the universe. Incidentally (and seemingly u