Time and Theology
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St. Thomas Aquinas in his Summa Theologica posits five proofs for the existence of God. A number of these follow the pattern below:
For every effect there is a cause.
Assume that there were an infinite progression of causes before now.
Then there would be no first cause, and therefore no resulting effects.
Thus it must be that there was a first cause, and that we call God.
I understand that there are supposed to be counterproofs to this, but I have not yet discovered them. Also, the counterproofs were supposedly developed by philosopers such as Hume, so they don't involve weird non-causality ideas and time-travel paradoxes.
It would seem to me, on the face of it, that St. Thomas is right. That there had to be a first cause at some first point in time and before that there was absolutely nothing: no space, no matter, no time, no nothing! Maybe the first point in time was the Big Bang.
With time-travel, of course you get major problems with causality. But it could still be that you can go anywhere AFTER the first point in time, because you are moving from one space-time coordinate to another, and where there is no time, there is no space-time, so no place to stop.
If time-travel is allowed, then it might work like a feedback circuit, where our current reality is an ever-shifting reality that is being modified by the effects of time-travellers. If the vast majority of space-time is unaffected by time-travel, then what we may be experiencing is negative feedback, i.e. a reality that is converging to a point of stability. If, however, time-travellers have an inordinate affect on the time-line (which seems to be the case if you just come up with a few scenarios such as someone killing Hitler before he starts the Nazi party, etc.) then what we are experiencing is a reality that is diverging to who knows where. We may think that we are experiencing a stable reality, but it could merely be an illusion caused by the fact that our memories are changed along with the rest of reality.
Our dreams could be artifacts of this ever-changing, ever-diverging reality. When we are unconscious (or less conscious) we could be more in touch with the divergence of realities caused by time-travellers.
Even though our current reality may be in continuous flux, this would still allow for morality, as we would always have a decision in front of us which we could make correctly or incorrectly. The only difference would be that our decisions are more important and must be made more rapidly since our reality is shifting so fast.
Also, with regard to that article by Deutsch: He assumes that time is not quantized. For if it were, then at some point he would run out of time and the world would end. By positing non-quantized time, he can live forever (at least by his perception) by slicing time into ever smaller slices. But if there is a smallest slice, then he is toast (literally!) Also, quantized time might add a little stability to a world populated by time-travelers by restricting them to discrete points of entry and exit. Also, it would provide "time" between the points in time for the world to reset based on the actions of time-travelers.
If time were quantized, then it might have some effect on causality since there now would be a disjointedness between a cause and its effect. This could allow for some uncertainty, and this may be a path for time travel, by moving between the points in time and covering up what would otherwise be a violation of causality with a haze of uncertainty.
Ultimately if people are able to travel back through time, they may want to travel BEFORE time, and their inability to do so may prove that there was a first time and a first cause and a God.
