On the B theory of time, every moment in time is phenomenally experienced as ‘now’ by reason not of some objective fact about tense, but by reason of the nature of our-selves. For example, Leibniz would say that the monad which we call our particular soul, simply has an appetitive quality in such a way that it naturally tends towards it’s end, and thus time is the phenomenal result of the monad’s inevitable appetite.
Now, while time travel is not logically possible if A theory is true, I wonder what sense can be made of time travel on B theory after analysis. Time travel (backwards) entails that I stand in some new relation to events which correspond to or precede moments (understood as conjunctions of states of affairs) which stand in the earlier-than relation to me. Not to me phenomenally, but to the sum of those things which have contributed to my experience. Not just the sum of all things I experience, but the subset of those experiences which I proximately recall and which form my conscious-relative past.
However, supposing that two-way determinism is logically possible on B theory, what if some event in the future caused (in a backwards way) me to remember things at some time t1 at which I would have stood in the earlier-than relation to? Is this sufficient for time travel? Phenomenally speaking, my self remembers a conjunction of events which stands in the later-than relation to me, or at least to that conjunction of events which I am currently disposed to experience. Plausibly this qualifies as time travel.
Moreover, consider that in a logically possible world I was caused to have in mind a set of memories which correspond precisely to future experiences I will have, but where the cause of my ‘memories’ is not those events which I remember, but a sheer accident of causal influences on my cognitive state of affairs. Thus, my memories of the future would be caused not by my experiencing the events which I will experience, but by accident. Would this qualify as time travel? If not, then why suppose that if my memories were caused by the events I will experience I have time travelled? Both situations provide me with or furnish me with revelatory and accurate insight into events which stand in a ‘later-than’ relation to me. Perhaps, as in epistemology, there has to be some kind of ‘reliabilist’ standard, such that the conjunction of events which I stand in the earlier-than relation to itself has to cause the ‘knowledge’ of those events in me in order for that transference of proximate experience to qualify as time travel. But of course, most of us do not think that knowledge is required for time travel, as we think we can imagine somebody time travelling from some future time, without retaining any memory of that future (This is why I said ‘those experiences which I proximately recall‘). Still, it is plausible to require some kind of causal relation for time travel between the conjunction of events which I recall and stand in the earlier than relation to (though I wonder what a Humean about causation would say about time travel then).
These thoughts lead onto other interesting questions, such as whether déjà-vu, if not a cognitive mistake on our part, is a form of mundane time travel?
I’ll need to reflect longer on making sense of time travel phenomenally, which seems to me required on B theory.