On the Nature of Experience in the Bare Theory

Quantum mechanic~ without the collapse postulate, the ~ theory, wa.~ proposed by Alben (1992) as a way of understanding Everett's relative-state fonnulation of quantum mechanics. The basic idea is to try to account for an observer's beliefs by appealing to a type of illusion predicted by the bare dteory. This paper respond~ to some recent objections to the bare thet)ry by providing a more detailed description of the sense in which it can and the sense in which it cannot account for our experience. Th~ bare theory, quantum mechanics without the collapse postulate but with the standard eigenvalue-eigenstate link, has several suggestive properties.! These properties tell us what an observer would report concerning her experience in various situations if the theory were true. Here I will discuss just one of these properties in some detail. Suppose that M is a perfect x-spin measuring device in the following sense: it is constructed so that the position of its pointer becomes perfectly correlated with the x-spin of a spin-l/2 system S without disturbing it. That is, M has the following two dispositions: (1) if S is initially in an x-spin up eigenstate, then M will report that the result of its measurement is x-spin up and will leave S in the x-spin up state