I wonder if I might raise a new topic for discussion here, one that has been bothering me for years. There is something very peculiar about time.
One of the most vivid aspects of our phenomenology is the feeling of there being a present, and our experience as being located in that present. It is always 'now'; but this time will soon be in the past, and a different time will be 'now'. Everyone understands this quite clearly, our language assumes it (tense structures, etc), people have invented nice neat logics of it, psychologists have measured it, etc.. The idea of being located in time, and somehow feeling that we are moving through it, is central to our culture, our laws, everything we experience and believe about ourselves. It underlies our notions of freedom and responsibility and tragedy and sin and redemption and...
However, there are two problems with this phenomenal 'now'. First, it seems to have no physical meaning. Second, and to my mind rather more significant, it doesnt actually make sense. It's not a coherent idea. We think of the 'now' as something like a dot moving along a line, or a river freezing over, or whatever your favorite analogy is; or if you prefer, think of 'now' as stationary and the world sliding from the future into the past. But all of these seem to involve something moving or changing. How could it be otherwise? The past certainly exists, in some timeless sense, since we can recall it; and the future presumably will eventually be past, so it also exists in the same timeless sense; and all of these times are 'now' at some time: so (in this same timeless sense) , 'now' seems to be inevitably 'moving' from past to future. But this is impossible, since (in this timeless picture) there is no time for it to move in. Movement or change of any kind requires a time to happen in, so if we take this timeless, Minkowskian, perspective (the way that relativity theory is often described for example) where will 'now' be placed? It has to be everywhen and nowhen. If the point needs emphasising, try to imagine what it would mean for the 'now' to move a bit faster. (How fast is it moving, anyway?)
I have developed frameworks for temporal reasoning which use all kinds of different intuitive ideas, including 'branching futures', coherent patches of spacetime, etc., and they all work in some ways and not in others; but none of them provide any meaning for 'now' other than a kind of spotlight scanning across the temporal dimension. That seems OK for 'here': if we have an internal map, then 'here' is just the place we happen to be at. But there is something deeply unsatisfying about a similar account for time. Think of staying still in space, and then try to imagine staying still in time in the analogous way. It doesn't make sense: why not?
This observation is not original, of course. Many great minds have worried about this, from St. Augustine to Meade to Schrodinger and Godel. Some SciFi has had fun with these ideas. For example, why couldnt there be other things whose 'now' dot is, say, 5 seconds after ours? I still havnt heard of a good explanation of what 'now' could possibly mean, however. Even though, like everyone else, it seems about as obvious as anything could be.
Seems that this might be a fairly central problem for a Science of Consciousness. Any comments?