Topics Time

Question Please pardon the awkward structure of this question; I am afraid the insuperable inadequacies of autodidacticism will prevent me from asking it clearly. What I want to know is, in a nutshell: Is the Past eternal? That is to say, it makes sense to make statements about the Present (if in fact there is a present; one sometimes reads there isn't) which take the form "X is the case." It also obviously makes sense to say, where t is some point in the Past, things like, "At time t, X was the case." But I'm much less confident that I'm allowed to have sentences like (if X is no longer the case but used to be at t, which is in the past) "At time t, X will always have been the case." And in fact I want very badly to say not only that but "For any X which once obtained, is obtaining, or will obtain, at any time T, will always once have obtained." I also want to believe this not only of propositions which once held, but also of all phenomena & entities which ever occurred & existed. (That they will always once have occurred/existed.)Is that true? My motive for asking the question, in case I have done so too clumsily to suggest how it might be answered, is what Russell somewhere calls the "curse of the philosophic temperament": that I have the religious fanatics's need desperately to believe noble or beautiful things about the universe I live in, coupled with the man of science's stubborn inability to believe anything I suspect may well be false. When I was very young, & went to Jesuit school, I expected the sort of actual immortality that was promised to me, but then I discovered that there's no reason whatsoever to suppose I even have/am a Cartesian "res cogitans"/"ego," let alone an immortal soul. Then I began to long for the sort of "poetic immortality" one finds in the Iliad or in Shakespearean sonnets, of being remembered & heroized after one's death; I decided that would be almost as good. Of course I realized later that, even if my own meagre achievements were somehow to merit such immortality, that history forgets, & even if it remembers, the human race won't be around until the end of the universe, & even if it is, they say universe itself won't last forever. So for several years now I've contented myself that even though I won't always be, or even be always remembered, I can still say "I will always have been." That's almost as good. But now I've been reading some of Goedel's letters & some modern-day philosophers of physics, & something very alarming springs to mind. If space & time are a unity, it stands to reason that since spatial positions are ordered only relationally (and not in priority or sequence; there being no absolute position or direction) that might well be true of temporal positions also. I even read an analysis of philosophical implications for phenomena in quantum physics which suggested that the best way to conceive of the Young experiment, & Heisenberg, & other such, is that the present or future actually influences & may even determine the past few microseconds! If the past isn't eternally fixed, then someday not just I, but things that actually matter, too, like poetry and math; heroism & ecstasy - will not only "cease to be" (I am resigned to that) but may someday never have existed at all! Dread over this possibility is tormenting me; I'm eating my whole weltanschauung from the inside out worrying about it. Please let me know if I'm still in the clear or if I've got to somehow part with even this little thing I still permit myself to believe & reconceptualize everything from the ground up. You have my profound gratitude for any insight you might shed on this issue. Earnestly, 'Bastian R.

Accepted:
March 13, 2008

Comments

You've raised lots of issues, but I wanted to single out one in particular. You seemed particularly worried by the possibility that there might be some sort of influence from present to past. The worry seemed to be that if someone did the wrong sort of monkeying around now or in the future, your past might be wiped out. That's a disturbing thought, but fortunately we needn't read Gödel et al that way. The trick is to distinguish between influencing the past and changing the past. Think of it this way: reality (or physical reality, anyway) just consists of the eternally-existing set of all events. On this picture, there's no question of a sort of "moving present" with events becomingpresent and then slipping into the past. There's just the set of eventswith all their many relations. You might find it useful to read what my fellow panelists Peter Smith and Jasper Reid had to say in response to question 2032 . Among the various relations are space-time relations, but there are also causal relations. It's just that we can't think of causing in the way that the "moving present" picture suggests as a sort of bringing-into-being.

On our usual way of thinking about things, causes are always unambiguously earlier than their effects. The speculations you're considering suggest that this may not be so -- that sometimes the direction of causation isn't the same as the direction of time. But the important point is this: the total set of events just is what it is, so to speak. If someone in the future exerts an influence on what I'm typing here, it's not a matter of their changing what I type; it's a matter of certain events in the future of my typing standing in a particular relation to all the events that make up my typing this reply.

This may be a little easier to grasp if we forget about changing the past and think about affecting the future. If my typing this "now" causes something to happen in the future, that doesn't mean I'm changing the future -- that somehow the future was one thing until I decided to type what I'm typing. Rather, it's that there's a cause and effect relation between events that come after my typing and the typing itself.

This picture seems odd when you first encounter it, but I dare say that it's the one most philosophers end up settling on. And if we accept it, then your past is safe; it simply is what it is, for better or for worse. Meanwhile, if you want to read an already-classic account of what it might mean to affect but not change the past, I recommend David Lewis's article "The Paradoxes of Time Travel." It first appeared in the American Philosophical Quarterly 13:145-52 (1976), and it's reprinted in his Philosophical Papers, Volume 2 (Oxford UniversityPress, 1986). But in any case, I don't recommend eating Weltanschauungen. It tends to produce intellectual indigestion.