time travel: presentism, going nowhere and personal time

["Alice Evans" <apyyae@nottingham.ac.uk>]

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woah there,

bernie, hold the fort,

a couple of things,

Yeh, presentism at first appears incompatible with time-travel; it seems non-sensical that one could travel back to the past if there is no past in existence. But, the so-called 'Nowhere Argument' fails to deny the compatibility of presentism and time-travel, for, "proving too much" , it appears to negate the coherence of presentism. As Keller and Nelson argue, even the ordinary passage of time, on a presentist account, requires some kind of travel to a non-existent temporal region. It seems uncontroversial to hold that there is nothing specific to ordinary passage that allows for the travel of non-existent times, which denies the same to past or distant futures.

i dont think this is a problem, once uve granted the basic presentist argument

secondly, on the issue of 'personal time',

Although (when time travelling) my reappearance precedes my disappearance in external time, the actuality of reappearance is only realised in my personal time. Keller and Nelson, denying the paradox, assert that "so long as we are aware that we are considering two different but compatible temporal sequences, sequences in which the same events can be ordered in different ways".  However, presentism's anti-reductionist stance on the direction of time illustrates the distinction between their accounts of external and personal time. Lewis argues that travelling into the external past is in one's personal future. For Lewis' account to work, personal time must be analogous to external time, but the presentist must deny their similarity. You seem to suggest that Keller and Nelson's interpretation of personal time no longer conforms to Lewis' requirements.

ok, so let's identify the presentist's conception of 'personal time'. The presentist uses "sequences of tensed statements describing causal and qualitative facts", rather than to "causal relations and qualitative differences between existent person-stages in the definition of personal time" (keller and nelson). Each personal future is constituted by past-tense causal statements, specific to the individual in question. This notion of personal future is thereby distinct from any idea of my external future, concerning future-tensed statements.

Personal time, for presentists, does not "play the role that time plays in the life of a common person" (Lewis) . Ok, suppose i want to go time-travel to the moment of my own conception, adopting a presentist stance, I would be unable to consistently declare that "in three minutes time I will watch my parents having sex". A presentist is limited to uttering that "watching the activity is in the future in my personal time". However, this new translation seems unsatisfactory. By diminishing the similarity between personal and external time, the presentist subverts personal time into an weird quality . My personal future plans, to view my parents having sex, consist in me once viewing their activity, courtesy of the causal time-machine. Thorough analysis of the presentist's account of personal time implies the fallacy that I am about to see my parents having sex. The time-machine is only capable of making it the case that I once saw my parents having sex, rather than that I will see such an event. 

whaddya reckon?

alice

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