Time  Bryn Mawr  college  Center for Science and Society Symposium,

from  http://serendip.brynmawr.edu/local/scisoc/time/chennotes.html    AUG 2007

The Philosophy of Time
Center for Science and Society Symposium, Fall 2003  "A Matter of Time"
February 5, 2003
Cheryl Chen
Department of Philosophy

Notes made available at talk




Two opposing pictures about the nature of time:

1) The Conventional View
"In daily life we divide time into three parts: past, present, and future. The grammatical structure of language revolves around this fundamental distinction. Reality is associated with the present moment. The past we think of having slipped out of existence, whereas the future is even more shadowy, its details still unformed. In this simple picture, the "now" of our conscious awareness glides steadily onward, transforming events that were once in the unformed future into the concrete but fleeting reality of the present, and thence relegating them to the fixed past." --Paul Davies, "That Mysterious Flow"
2) The "Block Universe" View
"Physicists prefer to think of time as laid out in its entirety - a timescape, analogous to a landscape - with all past and future events located there together ... Completely absent from this description of nature is anything that singles out a privileged special moment as the present or any process that would systematically turn future events into the present, then past, events. In short, the time of the physicist does not pass or flow." --Paul Davies, "That Mysterious Flow"
The debate between the conventional view and the block universe view is actually the combination of two debates in the philosophy of time:
1) Presentism vs. Eternalism
Presentism: only things in the present exist.
Eternalism: things in the past (e.g., dinosaurs) and future (e.g., human outposts on Mars) exist too.
2) The A-Theory vs. the B-Theory
A-properties: happening now, happened a week ago, happened in the past, will happen two years from now, happening in the future
B-properties: being two years after the 2000 Presidential Election, happening on July 4, 1776
The A-Theory: A-properties are genuine features of the world. Time passes. The present moment has a special status.
The B-Theory: A-properties are reducible to B-properties. Time doesn"t pass or flow. No moment in time has any special status.

Why many philosophers and physicists believe in the block universe view:
Philosophical considerations
1) McTaggart's argument
The A-properties are incompatible with one another, but according to the A-Theory, every position in time must possess all of the different A-properties. Since that leads to contradiction, the A-Theory must be false!
2) How fast does time flow?
If it makes sense to say that time passes, then it must also make sense to ask how fast time passes. Since that question doesn"t make sense, time doesn"t pass.

Considerations from physics: Einstein's Special Theory of Relativity

According to the Special Theory of Relativity, there is no such thing as absolute simultaneity. But if there"s no absolute simultaneity, then there is no objective fact about whether a particular event is in the present.
Worries about the block universe view:
1) "Thank Goodness That"s Over" (Arthur Prior)
When your headache finally stops after bothering you all morning, you say, "Thank goodness, that"s over!" But if the block universe view is correct, there is no such property as being over or no longer happening now. So what exactly are you thankful for?
2) The painful operation
You wake up and find yourself in a hospital bed. You know that you are in one of two situations:

i) You are about to undergo a very painful operation
ii) You have just had the painful operation, but were given a drug to make you forget the entire experience.
Which of these two situations would you prefer to be in? Commonsense says you should prefer (ii), but on the block universe view it shouldn"t matter which situation you"re in.
3) Fearing death
If the block universe view is correct, it is irrational to fear death. We apparently fear death because we believe that we will no longer exist after we die. But according to the block universe view, it"s not true to say that we exist now, but won"t exist any longer after death. Death is just one of our temporal borders, and should be no more worrisome than birth!

4) A general problem about explaining our actions
Our beliefs that presuppose the passage of time - beliefs expressed by terms that refer to A-properties - play an essential role in explaining most of our actions. Without such beliefs we would lack the resources to explain just about anything we do.

A mundane example: leaving my office to attend the time symposium This action makes no sense at all if I merely believed that I was due to give a talk at 7pm - my behavior only makes sense if I also believed that 7pm was coming up soon.

If scientists and philosophers succeed in convincing us to abandon our A-theory beliefs, just about everything we do or desire will be completely incomprehensible. So it"s hard to see how we could abandon those beliefs---even if scientists and philosophers give us reasons to do so!




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