Philosophy Colloquium
Lucas Dunlap
University of Maryland
Time Travel in Deutsch's Multiverse: The Knowledge Paradox, the Holmes Principle, and Shakespeare's Free Lunch

In a world where time travel is possible, could there be a closed loop of knowledge? Could a future Dunlap scholar bring me, in his time machine, the contents of my dissertation, so that I don't have to write it myself? In this paper, I address some conceptual issues surrounding Deutsch's solution to this paradox---known as the Knowledge Paradox---which stems from his influential framework for analyzing the behavior of quantum systems in the presence of closed timelike curves (CTCs). I argue that Deutsch's acceptance of the existence of the many worlds of the Everett interpretation in or to ensure that there is always an author of the dissertation (albeit in another world), creates a unique problem. The Many Worlds Interpretation commits Deutsch to believing that any history that is physically possible is actualized in some world. Among those histories, I argue, are ones which are indistinguishable in every way from worlds in which an Knowledge Paradox scenario plays out, wherein the dissertation exists, but was not written by anyone. Furthermore, in these worlds, the existence of the dissertation is not the result of time travel, but merely appears to be. So Deutsch's use of the Many Worlds framework to solve the Knowledge Paradox cuts both ways. It commits him to the existence of worlds in which the dissertation is genuinely a "free lunch"---it exists, but was not the result of the intellectual effort of rational beings---which is exactly the situation Deutsch was trying to avoid.

Wednesday, January 29, 2014

Skinner 1115