Huw Price, Retrocausality--what would it take?

Conférence plénière du 21 juillet - CLMPS 2011 / Plenary lecture, Thu. 21 July - CLMPS 2011
Some writers argue that retrocausality offers an attractive loophole in Bell’s Theorem, allowing an explanation of EPR-Bell correlations without “spooky action-at-a-distance.” This idea originated more than a decade before Bell’s famous result, when de Broglie’s student, Olivier Costa de Beauregard, first proposed that retrocausality plays a role in EPR contexts.
The proposal is difficult to assess, because there has been little work on the general question of what a world with retrocausality would “look like”—what kinds of considerations, if any, would properly lead physicists to conclude that we do live in such a world, and what that would mean, in terms of the structure and use of physical models. In this talk I begin with a brief discussion of these general issues, with the aim of bringing the more specific question as to whether quantum theory implies retrocausality into sharper focus than has hitherto been possible.
Against this background, I then consider the suggestion (made by Costa de Beauregard himself, amongst others) that time-symmetry counts in favour of retrocausality in the quantum case. I show that this is true under some assumptions about quantum ontology but not others. In the remaining cases, the most that can be said is that it remains an open question whether the quantum world is retrocausal, even if we assume time-symmetry. Contrary to conventional wisdom, however, there seems to be little justification for the standard assumption that the quantum world is not retrocausal. At present, this assumption seems to be dogma, not science.