The Fabric of Reality

Deutsch argues that reality is best understood through four strands of explanation that must be taken together: quantum physics in the many-worlds interpretation, the theory of computation, the theory of evolution, and epistemology in Popper's form. His claim is that each strand is incomplete alone and that together they form a coherent account.

His treatment of quantum mechanics is the most contested. Deutsch is a leading advocate of the many-worlds interpretation and argues that it is the only interpretation that takes the mathematics literally, and he uses interference experiments and the operation of quantum computers, on which he did foundational work, to argue that the alternative interpretations require the universe to behave as though other outcomes exist.

The computation strand covers the Church-Turing principle and Deutsch's extension of it, arguing that a universal computer can simulate any physical process, which places constraints on what physical reality can be. The evolution strand covers replicators and knowledge, arguing that knowledge is a form of information that causes itself to be preserved. The epistemology strand follows Popper, holding that knowledge grows through conjecture and criticism and that explanations rather than predictions are the goal of science.

The book is demanding and the physics assumes willingness to follow unfamiliar arguments. The many-worlds interpretation remains a minority position among physicists, and readers should know that Deutsch presents a contested view as settled. The Beginning of Infinity develops the epistemology further and is the better book for readers interested primarily in that.