In this accessible yet thought-provoking book, readers will encounter everything from Plato's allegory of the cave and John Wheeler's it-from-bit hypothesis to how mind and body might interact in virtual worlds, whether reality is a mathematical structure, and whether we might just be Boltzmann brains floating in a dream world. Chalmers also tackles techno-centric questions like whether smartphones extend our minds, whether the Internet is making us smart or stupid, the threat of deepfakes and alternative facts, and whether there can be an objective reality in a multiverse of virtual worlds.–Jennifer Ouellette "Ars Technica"