Presuppositions and Science

I heard on a podcast a theist say that he had a problem with Victor Stenger.  The critique was phrased something like, that Dr Stenger put his atheism first in his explanations, that he has a presupposition against against using God as an explanation, a presupposition against the supernatural.  Something struck me as odd about this perspective, and then I realized that one never hears this sort of perspective in scientific circles.

Why not?  I think it’s because, in science, it is recognized that the natural world will correct any wrong presupposition…the truth will out.  So, if someone has a presupposition, just let it ride out and see if it works.  Einstein had a presupposition for a static universe – he even “corrected ” his theory to get rid of the dynamics when it was pointed out to him that that was a consequence.  Once the data came in that was best explained with a dynamics universe, he modified the theory and said it was a big mistake.

Another example comes from my own experience teaching astronomy.  For years I taught the prevailing wisdom that there were two possibilities for the end of the universe.  Either the expanding universe, initiated at the Big Bang, would have enough mass to collapse again in a Big Crunch or it would expand forever, slowing but never stopping.  It was never on the radar that it could be accelerating, and had anyone suggested it, I would have said it was unreasonable.  Of course the universe doesn’t care about my bias, lack of imagination, or presupposition and it does appear to be accelerating nonetheless.

So, if someone has a presupposition against God as an explanation, indulge them!  If they are wrong, then at some point it will make a bad prediction and fail.  If not, then we’ve learned that, for the thing explained, the concept of God is not necessary.  Don’t complain about the presupposition.  Know that the truth will out, eventually.  On the other hand, I would love to know what predictions the God theory makes (not post-dictions), so that it can be tested.

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About brianblais

I am a professor of Science and Technology at Bryant University in Smithfield, RI, and a research professor in the Institute for Brain and Neural Systems, Brown University. My research is in computational neuroscience and statistics. I teach physics, meteorology, astonomy, theoretical neuroscience, systems dynamics, artificial intelligence and robotics. My book, "Theory of Cortical Plasticity" (World Scientific, 2004), details a theory of learning and memory in the cortex, and presents the consequences and predictions of the theory. I am an avid python enthusiast, and a Bayesian (a la E. T. Jaynes), and love music.
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6 Responses to Presuppositions and Science

  1. Tim says:

    I have a slightly off-topic question for you that occurred to me yesterday. I came to my mind just now because you mentioned the expanding/accelerating universe.

    I remember reading in a book — I think one of Brian Greene’s — that for some time after the big bang, objects (or regions of space) may have effectively move apart from one another faster than the speed of light, without any matter actually moving that fast, because the intervening space itself was expanding.

    So it occurred to me… if space is still expanding today (a left-over from the Big Bang), and objects are also moving away from us (also a left-over from the Big Bang), might it seem from our point of view that they are *accelerating* away from us, even though they might actually be decelerating due to gravity?

    Say I hit a baseball very, very hard and give it a velocity of 100 kps. That’s well outside Earth’s escape velocity. Immediately after hitting it, I examine it with a telescope, measure it’s redshift, and confirm that it’s moving at 100 kps. In a few days, I measure it again and my redshift measurement tells me it’s moving away from me at 101 kps!

    I could explain this by positing some kind of anti-gravity force that’s pushing it away (accelerating it), but I could also explain the observation by positing that the space between myself and the ball is expanding. Even if the ball was decelerating due to gravity, and even if the expansion of space were decelerating due to gravity or some other force, the cumulative effects as the ball moves farther and farther away from me (more expanding space between us — like a compounding interest rate) might make it look to me like the ball is accelerating.

    Measuring redshift is, after all, a measurement of the stretching out of the light waves due to the velocity of the observed object, but might the same kind of stretching out be caused by the expansion of space? The cumulative effect could then look like acceleration, when really both the object’s velocity and the expansion rate were decreasing.

    So, what do you think of this idea?

    • brianblais says:

      “if space is still expanding today (a left-over from the Big Bang), and objects are also moving away from us (also a left-over from the Big Bang), might it seem from our point of view that they are *accelerating* away from us, even though they might actually be decelerating due to gravity?”

      Unfortunately the magnitudes are way off. For distant objects, the spreading of space is way larger than any relative velocity within that space. You can see that as a distribution of redshifts at known distances. Thus, it is easy to distinguish these two types of motion, and it becomes less and less relevant for more distant (and thus more red-shifted) objects because the magnitudes of the shift are much larger due to space-stretching than motion within the space.

      Does that make sense?

      • Tim says:

        If that’s the case, then how do we know the objects themselves are accelerating away from us?

      • Tim says:

        In fact, if every object in the universe were standing perfectly still, but space itself were expanding, wouldn’t this give any observer the impression that everything in the universe were accelerating away from him?

  2. brianblais says:

    (reached the depth of reply, so I’m replying here)

    “In fact, if every object in the universe were standing perfectly still, but space itself were expanding, wouldn’t this give any observer the impression that everything in the universe were accelerating away from him?”

    No, actually. What we have is really a snapshot of each object, not following any given object over time to see a change in that. For example, if we measure the redshift of a distant galaxy we can derive a speed. If we go back years later, do the same thing, we get the same speed. However if we measure the redshift of a galaxy twice as far away as that one, we determine that it is moving twice as fast away. This isn’t evidence of acceleration, it is evidence of a *constantly* expanding space. You can do this on a balloon. Blow it up a little, and put a bunch of dots labeled A, B, C, etc… Measure all of the distances between them. Blow the balloon up more and you’ll find that all the points move away from each other, and the ones that were initially farther away from each other have moved more than the ones initially closer.

    To determine acceleration, we need to see a deviation from this pattern of X times farther away = X times faster. If it is X times farther away = less than X times faster, that is evidence of acceleration. The observed evidence for this kicks in well into the billions of light years away, and is a small effect. See this for a nice summary:

    http://www.supernova.lbl.gov/PhysicsTodayArticle.pdf

  3. seeker says:

    Brian,

    Although many intelligent design advocates may argue that excluding God from science is just an unjustified bias, presumption, or a priori assumption, I think it may actually be nothing more than the tacit realization that even after well over two millennia “Goddidit” has never, ever had any real success in science.

    If supernatural explanations have never, ever been shown to be correct, while materialistic explanations are routinely shown to be correct, then common sense would probably lead us to expect that looking for supernatural explanations for any still-unsolved riddle is likely to be a waste of time. I think that historical reality is why mainstream scientists don’t pay much attention to creationists, and it seems to be a very sensible approach IMHO.

    Finally, your apparent attempt to exclude retrodictions from consideration was probably unnecessary. Not only does “Goddidit” not logically lead to any testable predictions, it probably doesn’t logically lead to any testable retrodictions either. An omnipotent God is by definition compatible with any logically possible outcome. Since any outcome actually observed in nature must by definition be logically possible, that means that *no* observable outcome can conflict with the existence of an omnipotent God. Scientific claims must be testable, which means that there must be some logically conceivable outcome that conflicts with the God hypothesis. Probably no observable outcome can be in conflict with an omnipotent God, and that probably means that Goddidit is not a testable hypothesis, regardless of whether we’re talking about predictions or retrodictions.

    For example, Goddidit is perfectly compatible with the fossil record in its currently hypothesized order, in a completely reversed order, or with no order at all.

    Goddidit is also perfectly compatible with the currently hypothesized pattern of nested hierarchies of organisms, with a completely different pattern, or with no pattern at all.

    People frequently talk about scientific “predictions,” but I think that the term “testable statements” is a better term, because it acknowledges the fact that science can validly be used to make statements about the past as well as about the future. Forensic science, archaeology, and paleontology come readily to mind here.

    So don’t be afraid to open up the field of retrodictions to the creationists. My prediction is that they still won’t have any success.

    The title of Stenger’s book about “God: The Failed Hypothesis” is a bit of a misnomer, because the hypothesis that Stenger used in that book assumed that there were some outcomes that were beyond the ability of the “God” in his definition. But the “God” in Stenger’s definition is not the only possible God. A genuinely omnipotent God, by definition, can do all things that are logically possible. Stenger’s hypothesis did not really address that issue. (But the book was still pretty good, IMHO.)

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