I sent something on this privately to Garry. But basically, it is
the argument, originally due to the physicist Brandon Carter and greatly
expanded by the philosopher John Leslie in such books as Universes and The
End of the World, that the end of the world might be expected to come sooner
than one would have thought, because otherwise we would be unusually early
in the human race (e.g., if it goes on at present or higher population
levels for many centuries, so the the number of people after us is much
greater than the number of people before us, which has been extimated at
50-100 billion).
>>
>> I appreciate the information that "A-theorists believe that there is
>>an ontological (not merely epistemic) asymmetry between past and present, on
>>the one hand, and the future on the other. The past and the present are
>>real, while the future is not." However, I am slightly confused, since I
>>thought Leslie told me today that A-theorists believe the present exists but
>>neither the future nor the past. Are such people also A-theorists, or is
>>there actually yet a different name for those who believe that only the
>>present exists?
>
>There are, in fact, two versions of the A-theory. One is more commonly
>called "presentism," for it holds that only the present is real. Sometimes
>this is referred to as "temporal solipsism." The more prevalent version of
>the A-theory holds that both the past and the present are real, but the
>future is not.
>
>> I also appreciate the point that "The fundamental issue here is not
>>what can be known but what exists. There is always the danger of conflating
>>epistemic with ontological claims." But now I am curious as to what the
>>evidence is that leads an A-theorist to claim that the future does not
>>exist. Also, for an A-theorist who believes that the past as well as the
>>present exists, what is the evidence that the past exists but not the future?
>
>Well, it is just the A-theory itself which claims that the future is not
>real. If one is an A-theorist, then ipso facto one believes that there is
>the ontological asymmetry in question. If, however, you are asking what
>evidence or argument is there for the A-theory, see below.
I intended to ask what the argument is for the A-theory, so I'll
consider it below.
>> In Garry's later posting (Thu, 13 Nov 1997 09:18:07 -0700) on God
>>and time he states, "I think we absolutely must distinguish between
>>metaphysical time (God's time) and the measured time of the physical
>>universe. Even if we cannot do better than an operationalist notion of
>>physical time, we still are not forced to give up the idea of absolute
>>simultaneity." Similarly, in his posting of Fri, 14 Nov 1997 21:55:45 -0700
>>he notes, "Even if people persist in moving relativistically, it seems that
>>we only are forced to give up our knowledge of simultaneity, not the thing
>>itself." I think I agree that I don't see (at least yet) how to force an
>>A-theorist to give up the idea of absolute simultaneity, but I would like to
>>ask what the evidence is that there is any such thing. Also, of what use is
>>the idea if it can never be known?
>
>I suspect that behind this there is the shadow of operationalism, but I
>neeed to let you address that for yourself, Don. As a critical realist, I
>am content to admit that there are realities which we do not--and perhaps
>cannot in principle--know. I would be quite loath to adopt the
>pragmatist's approach either, and see truth as only that which I can use.
>I believe that there is an infinite number of true propositions which are
>of no "use" whatsoever.
There is probably at least a shadow of operationalism in my query,
but I would not object to postulating entities that we cannot know (at least
directly) or cannot use, so long as they give a simpler picture of reality
that is consistent with what we do know. But if the entities just
complicate the picture and have absolutely no testable consequences, then I
would see no reason to postulate their existence.
>As to "evidence" that there is such a thing as absolute simultaneity, the
>evidence is that it is entailed by the A-theory, just as the evidence for
>many things in physics is that they are entailed by the best current theory
>(e.g. what is the evidence for 10- [or 23-] dimensional superstrings?). No
>experimental evidence is available at this time. Conceivably such evidence
>could become available, or a better theory could come along which would
>shed new light on the issue in question and allow is to redefine,
>reconceptualize, or abandon it.
In view of my paragraph above, is there any way in which absolute
simultaneity simplifies the picture or has any testable consequences? In
other words, does it have any explanatory power?
>> Perhaps a clue to a possible motivation for an A-theorist is given
>>by Garry's final words of his posting of Fri, 14 Nov 1997 21:56:12 -0700,
>>"If temporal becoming is not a real feature of the universe, but is only
>>psychological, then I believe that it is difficult to give any real meaning
>>to the notion of causation, let alone to escape the fatalist dilemma."
>>Since I myself don't find these supposed problems with the B-theory nearly
>>sufficient to cause me to adopt the A-theory, I am curious as to whether
>>there is any more positive evidence for the A-theory than this.
>
>While you have often spoken of "evidence" above, I should make it clear
>that a metaphysical theory will be supported by certain arguments, and will
>be evaluated by the strength of those arguments, as well as by its power to
>explain certain phenomena (not unlike scientific theories in this regard).
>
>I'll offer three lines of argument which support the A-theory. I will only
>offer a summary of the arguments here, for reasons of space (the summaries
>are long enough!):
>
>(1) Common linguistic practice, while not determinative of reality (as some
>postmoderns would say), certainly reflects reality. The use of tensed
>language is evidence that temporal becoming is real and that temporal
>indexicals cannot be reduced to tenseless language plus a token-reflexive
>reference to the time of the utterance. The A-theoretic statement, "A bomb
>will explode in the station five minutes from now" conveys information that
>the B-theoretic statement, "A bomb explodes in the station five minutes
>later than the time of this utterance" does not, for the first will
>certainly be action-guiding while the second will not be, unless
>accompanied by additional information about the time of the utterance and
>what time it is now, a A-determination. Furthermore, expressions such as
>"Thank goodness that's over!" uttered after, say, a root-canal, are
>incomprehensible if reduced to the B-theoretic expression "Thank goodness
>the time of this uterance is later than the time of the root canal." Such
>example could be multiplied. There are admittedly deep issues in the
>philosophy of language involved here, but the basic point is this: human
>thought and action depend inescapably upon tensed determinations. The
>ineliminability of tense in guiding our beliefs and actions explains why
>tense is so pervasive in common linguistic practice. I suggest that this
>is an argument for the conclusion that reality itself is tensed--that is,
>that time is dynamic (A-theoretic).
First, I might try to say what Sidney Coleman said on the final
episode of the TV series Stephen Hawking's universe, to the effect that our
language developed to handle our normal experience, and so we should not
expect it to handle all that we learn in science. (Coleman was referring to
quantum theory, but I could also take it as referring to time as the fourth
dimension that is linked up with space in a nonseparable way.)
Second, I don't see the difference between "A bomb will explode in
the station five minutes from now" and "A bomb explodes in the station five
minutes
later than the time of this utterance," except that the latter sounds very
stilted. "Now" just means "the time of this utterance," at least in
B-theory. Anyone who hears the second utterance and understands it
presumably seeks, within five minutes of the time of the utterance, to leave
the station (assuming that the person does not want to be in the station
when the bomb explodes, etc.). "Thank goodness
the time of this utterance is later than the time of the root canal" also
seems to make sense to me, because it presumably implies that at the time of
this utterance, there is less pain than at the time of the root canal,
something for which the person at the time of the utterance is thankful.
(Of course, it also implies that at the time of the root canal, there is
more pain, and so one might ask why one should be thankful for that, but
maybe it just means that he or she is thankful that not all times are so
painful as the time of the root canal. In any case, it seems no worse than
saying, after learning that one had missed an airplane flight which
subsequently crashed, "Thank goodness it wasn't I that was killed," which
also seems to imply that one is thankful that someone else was killed.)
>(2) An entity may persist in in time by enduring, in which case it is
>conceived as being wholly present at any time at which it exists, or by
>perduring, in which case it is conceived as being spread out through time,
>and only a part of it--a temporal part--is present at any time at which it
>exists. A strong argument can be made that only enduring entities exist in
>A-theoretic time, while only perduring entities exist in B-theoretic time.
>Another argument then establishes that consciousness is only possible for
>enduring entities. Hence, if persons are characterized by (among other
>things) persisting consciousness, then they are enduring things, and time
>is A-theoretic.
What is the argument that consciousness is only possible for
enduring entities? I suspect that I would be very sceptical of such an
argument.
>(3) A pervasive part of human experience is that our experience is present
>tense. (Of course, my present-tense experience of seeing the sun is the
>experience of the sun as it was some 8 minutes ago; nevertheless, the
>experience per se is present.)
I agree.
>But according to the B-theory there is no
>present-tense.
There can be conscious experiences, each one of which is present
tense (at least relative to the same experience itself).
>Further, consider the class of experiences of mentally
>tokening a sequence, such as counting to 50 when playing hide-and-seek, or
>counting sheep to fall asleep, or mentally playing the score of a piano
>sonata, and so forth. Now whatever might be said about events in the
>external world, it does not seem possible to avoid the conclusion that I
>experience each successive member of the sequence as first future, in that
>I am at least tacitly aware of its "coming," then as present, and then as
>past ("I got past the D-flat minor diminished seventh chord this time!").
>My experience is of the successive passage of mental states, and is
>A-theoretic in nature. But isn't it open to the B-theorist to reply that
>my experience of the "passage" of these mental states is itself merely
>psychological and not reflective of any ontological reality? Yes, but
>only at the pain of infinite regress which does seem to be vicious, for the
>psychological states themselves pass in succession, and would need then
>ever-higher-order states to explain the apparent succession of the
>lower-order states.
I agree that many conscious perceptions, experiences or
psychological states (whatever one wishes to call them; I'm not making a
distinction between these terms) have contents that can be divided into a
perceived anticipation of the future, a perceived awareness of the present,
and a perceived memory of the past. Furthermore, a perception can even
contain a perceived memory of an event along with perceived older memories
of anticipating the event. However, I'm not sure one would have to say the
psychological states themselves pass in succession. (In classical physics
one might have a theory of time in which they are ordered in time, but in
quantum theory I don't think this is necessarily so.) The psychological
states could just exist, without necessarily "passing" or even being ordered
in time.
>One additional point should be made. If time is dynamic, we need a theory
>of time which explains its dynamic character as well as its direction. We
>need to be able to explain why time "flows" at all, and why it flows in the
>direection it does. A causal theory of time answers both questions. A
>realist theory of causation can explain why a state of affairs at time t
>can bring about another SOA at time t+1. And if formulated properly, a
>causal theory can rule out both causal loops and backward causation (the
>arguments are significantly different) as being metaphysically impossible,
>thus explaining the direction of time (a notable feature of a causal theory
>of time, since as we know by now, arguments from statistical thermodynamics
>have shown that entropy--which used to be everyone's favorite arrow of
>time--cannot do the job).
I'm not sure what you mean by time being "dynamic." I could say
that spacetime is dynamic in general relativity, since the metric obeys
Einstein's equations, but I'm a bit doubtful that that is what you mean. If
you did, one could just say that general relativity is the theory that makes
time dynamic. (Of course, this is almost certainly not the final theory of
time, not least because it does not take into account quantum theory.)
However, I'm not sure I would say that time "flows" in this theory, or that
it has any direction. The equations of motion of fields in spacetime imply
that there are correlations between the fields at one time and at another,
which is what we interpret as a causal relation, but this goes equally well
in either direction (future to past as well as past to future).
>> Since John Leslie told me there are plenty of respected A-theorists,
>>I am really just confessing my ignorance of what their arguments are, so now
>>I am taking the lazy man's approach (or am I trying to be more efficient?)
>>of trying to find what their arguments are without having to take the bother
>>of actually reading philosophy texts on what I have thought was a very
>>implausible view (especially if the past is supposed to exist but not the
>>future; saying that only the present and neither the future nor the past
>>exist seems more nearly plausible to me). So perhaps Garry can enlighten me.
>>
>> Don Page
>
>I doubt that there was any enlightenment above! ;^) Metaphysical arguments
>are not easy to abbreviate. I am disturbed by the fact that almost all
>cosmologists I know are B-theorists (like you and Leslie and Davies and
>Tipler and others), but at the end of the day, I think this is a
>philosophical and not a physical question. But I can recommend a couple of
>good texts, if you are interested! (And I am enjoying the discussion.)
I would appreciate your recommendation of some good texts, though I
won't promise to read them :). I enjoy a direct discussion more!
>
>Garry DeWeese
>
Don Page