Wednesday, May 9, 2012

Metaphysics > Physics

Feser's next job is to answer the question, "How is change possible?" The answer lies in Aristotle's distinction between actuality and potentiality (or "act" and "potency" in the traditional terminology). Thus, a rubber ball is actually blue, round, and bouncy. But it is potentially "red (if you paint it), soft and gooey (if you melt it), ... and so forth."

This distinction is the basis of the principle "Whatever changes is changed by something else." Aquinas's First Way of proving the existence of God begins from this principle, so it is an important one for Feser. He writes,

Second, and as indicated already, Aristotle holds that even though a thing's potentials are the key to understanding how it can change, this is not the end of the story. An outside source of change is also necessary. For potential gooeyness, say, precisely because it is merely potential, cannot actualize itself; only something else (like heat) could do it. Consider also that if a potential could actualize itself, there would be no way to explain why it does so at one time rather than another. The ball melts and becomes gooey when you heat it. Why did this potential gooeyness become actual just at that point? The obvious answer is that the heat was needed to actualize it. If the potential gooeyness could have made itself actual all by itself, then it would have happened already, since the potential was there already.

So, no potential can actualize itself, and in this sense anything that changes requires something outside it to change it.
 The "So" in the last sentence indicates that Feser thinks he has established his conclusion - the principle "Whatever changes is changed by something else" - in the previous paragraph. I quoted the entire paragraph so you can be sure I didn't leave out anything important. But that argument (I claim) is deficient.

The example of the ball is just that - an example. It can't be proof of anything. There's no way to argue from "In this example the thing changed is changed by something else" to "Whatever changes is changed by something else." That would be a fallacy: "One A has B, therefore all A have B."

So the argument must lie in the first part of the paragraph. Here's how I read that argument.
  1. For a change to happen, a potentiality must become actual.
  2. When a potentiality becomes actual, either
      • it actualizes itself, or
      • nothing actualizes it, or
      • it is actualized by something else.
  3. A potentiality can't actualize itself (because it is only potential, not actual).
  4. A potentiality can't be actualized by nothing (because then there would be no way to explain when the change occurs).
  5. Therefore, a potentiality must be actualized by something else.
 My complaint is with (4). This step only works if you assume that there is always a way to explain when a change occurs. But what if there isn't?


This might seem a strange complaint - unless you know something about quantum mechanics. (This is where my argument with the folks at Victor Reppert's blog began.) Since this post is already getting long, I'll leave the explanation to the next post.

8 comments:

  1. I think the crux of his argument is this: "Consider also that if a potential could actualize itself, there would be no way to explain why it does so at one time rather than another."

    Which is exactly what we see at the quantum level. Oops. No explanation is available for why certain events happen at one time rather than another. Deal with it, Feser. Feser tries to smuggle in a principle of sufficient reason, but I can recall no argument for it.

    Later in the book you will find an argument about why there can be only one God. It's something like there can't be two Gods because then we could not tell one from the other. It really is that bad. Look for it.

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  2. Quantum mechanics do not appear to pose any problem for the principle of causality. In fact, quantum physics and the Aristotelian concepts of prime matter and pure potentiality actually fit in quite nicely with the indeterminate nature of quantum physics.

    Quantum Physics vs The Principle of Causality

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  3. Thanks for the link, hylemorphist, that's an interesting article. However, it doesn't answer the question: What actualizes the change when an excited electron drops to a lower level?

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  4. The whole discussion in terms of whether "a potential could actualize itself" is crooked.

    What Aquinas, and Feser, are talking about are the potential status of an existing, actual, physical system - its phase space. The question is therefore whether the state can change without something external getting into the picture. And clearly the answer is that yes, *logically* it can change without any need for an external influence.

    The whole division into "actualizes itself" is misleading metaphysics. What exists changes, and this change can be described - that is all. The division into causes is a division we make, it is an arbitrary division that doesn't really exist in reality - and that's precisely why you won't find "Cause" in physics, only phase states, actual states, and the Hamiltonians that describe how the actual states change in time. (Or Lagrangians, but that's just a different framework.)

    What "actualizes" the change of location of an isolated Newtonian ball, moving in a straight line at constant velocity? Is it the ball itself? The existence of the ball at a certain velocity and location at a previous time? Or perhaps even at a later time? Or is it "Nothing"? Or is it the surrounding laboratory? The question is meaningless, an empty and arbitrary metaphysics. What exists changes - that is all.

    This change can be random, as in QM, or deterministic, as in classical mechanics. But even in a deterministic setting, what changes need not change due to the influence of some *other* thing. The rules of the change can very well maintain that, e.g. "After N seconds at state X, the system will change to state Y". This is a *logical* point, independent of what physics actually holds. In practice, in the actual classical mechanics that holds in our world, closed systems do indeed change.

    Feser's metaphysics is an utter failure. You don't need QM to show it, you don't even need classical mechanics to show it. It's just dogmatic - asserting what the physical truth is with no empirical or logical basis.

    Yair

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  5. Yair, I think you've put your finger on it. We physicists just don't find this metaphysics to accord with our own. But I think it's interesting to grant Feser his starting point, and see if the argument works given that starting point.

    However, I don't think you're giving his point of view as much credit as it deserves. It's not just a matter of what's logically possible - as you say, it's clear that there are logically possible relations that violate the principle. It's supposed to be a metaphysics based in what we actually know about how the world works.

    That's why I think QM is relevant: if it's about the way the world actually works, it has to be consistent with what we know about QM.

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    Replies
    1. There is no such thing as a philosophy free science or a science that is free of metaphysics. There is only a science who's philosophical or metaphysical presuppositions are unexamined.

      Your QM argument is nothing but a "gap" argument. No different & no better then the "gap" arguments one might find over at the DISCOVERY INSTITUTE so called.

      "un-caused events", Paley's "god" or Invisible Pink Unicorns.

      Like it or not Prof Oerter you are an Atheist who believes in magic.

      Thomists/Aristotelians by definition cannot believe in magic.

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  6. Yair, I think you've put your finger on it. We physicists just don't find this metaphysics to accord with our own. But I think it's interesting to grant Feser his starting point, and see if the argument works given that starting point.

    However, I don't think you're giving his point of view as much credit as it deserves. It's not just a matter of what's logically possible - as you say, it's clear that there are logically possible relations that violate the principle. It's supposed to be a metaphysics based in what we actually know about how the world works.

    That's why I think QM is relevant: if it's about the way the world actually works, it has to be consistent with what we know about QM.

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  7. From my perspective thus far, Professor Feser's arguments generally seem to wander too close / into the "turtles all the way down" scenario.

    He posits "the heat" causing the "gooeyness" of the ball ... but then you need to explore the circumstances that created the heat AT the right temperature (which I suppose creates the "moment" etc...) and on, and on...

    Is this a problem of semantics? Physics does explain why the ball gets "gooey" when a certain amount of "heat" is applied.

    Do we need any more than that? Even if we found "more than that" would it help humanity answer questions, or just answer the argument?

    I suppose "quibbling" over the minutiae is what I'm trying to point to here. Maybe, just maybe, Thomism needs to be ignored and society needs to move on to more important things?

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