This book defends the view that the Everett interpretation of quantum theory, often called the ‘many worlds theory’, is not some new physical theory or some metaphysical addition to quantum theory, but simply quantum theory itself understood in a straightforwardly literal way. As such ‐ despite its radical implications for the nature of our universe ‐ the Everett interpretation is actually the conservative way to approach quantum theory, requiring revisions neither to our best theories of physics, nor to conventional philosophy of science. The book is in three parts. Part I explains how quantu ... More

This book defends the view that the Everett interpretation of quantum theory, often called the ‘many worlds theory’, is not some new physical theory or some metaphysical addition to quantum theory, but simply quantum theory itself understood in a straightforwardly literal way. As such ‐ despite its radical implications for the nature of our universe ‐ the Everett interpretation is actually the conservative way to approach quantum theory, requiring revisions neither to our best theories of physics, nor to conventional philosophy of science. The book is in three parts. Part I explains how quantum theory implies the existence of an emergent branching structure in physical reality, and explores the conceptual and technical details of decoherence theory, the theory which allows us to quantify that branching. Part II is concerned with the problem of probability, and makes the case that probability, far from being the key difficulty for the Everett interpretation, actually makes more sense from a many‐worlds viewpoint. Part III explores the implications of an Everettian perspective on a variety of topics in physics and philosophy.