Abstract: Sixty years on there is still deep division about Everett's proposal. Some very well informed critics take the whole idea to be unintelligible whilst there are important disagreements amongst supporters. I argue that Everett's fundamental and radical idea is to do with metaphysics rather than physics: it is to abolish the physically possible/actual dichotomy. I show that the idea is intelligible via a thought experiment involving a novel version of the mind-body relation which I have already used in the defence of semantic internalism.
The argument leads to a fission interpretation of branching rather than a “divergence” interpretation of the sort first suggested by David Deutsch in 1985 and more recently developed in different ways by Simon Saunders, David Wallace and Alastair Wilson. I discuss the two metaphysical problems which fission faces: transtemporal identity and the identification of probability with relative branch measure. And I claim that the Born rule applies transparently if the alternative mind-body relation is accepted. The upshot is that what Wallace calls the Radical View replaces his preferred Conservative View, with the result that there are some disturbing consequences such as inevitable personal survival in quantum Russian roulette scenarios and David Lewis’s suggestion that Everettians should “shake in their shoes”.
