The Quantum Challenge

I have saved the issue of quantum mechanics for last, as it is the most difficult. Prof. Feser makes some very good points in his remarks on quantum mechanics and causality. To respond to these points fully, I would have to present a complete alternate account of causation and physical law, which I have neither the knowledge nor the time to do. (But see the paragraphs in parentheses below for a hint of how such an account might go.) But let me try to clarify my quantum challenge.

A point that I perhaps didn't make clear enough in my original post on the quantum challenge: the challenge comes primarily from the quantum phenomena themselves, and only secondarily from the theory of quantum mechanics. Regardless of what the theory says about the electron transitions that produce line spectra, the very existence and pattern of those transitions is what the Thomist must reconcile with his metaphysical views. Since Feser's response is directed at the theory of quantum mechanics and how it answers different questions than the metaphysical ones, that response is to some extent missing the point.

As an analogy, suppose someone were to discover a kind of pebble that behaves in every way like an ordinary pebble, except that, at some time during its existence, it suddenly turns into a puddle of goo. No external cause can be found for this strange transition. So, we look for an internal cause: some sort of internal structure that could explain the change. But slicing the pebble open reveals no such structure: the pebble seems to have a very simple composition. So we look deeper: perhaps there is some chemical change going on? But no such chemical changes can be found. And as time goes on, scientists continue to be unable to identify any cause of the change.

My claim is that the existence of a class of pebbles like these would call into question the principle "Whatever changes is changed by something else." And this would be the case regardless of any theoretical description of the puddling pebbles that scientists were able to work out. One could always hold out hope that an explanation of the change would someday be found. Or one could attempt to subsume the phenomenon under the principle by, for instance, pushing the "something else" that causes the change back to whatever brought the pebble into existence in the first place. But you can't claim that these pebbles are irrelevant to the principle.

My second point is that, whatever you make of the connection between natural laws and causes, it can't be true that the former is irrelevant to the latter, as Feser claims. This is clear even from his own book: every example of causation that Feser gives is implicitly or explicitly dependent on laws of nature.

For example, on p.54 he considers a rubber ball that becomes gooey when heated, and says that the heat is what actualizes the potential gooeyness of the ball.

This makes no sense unless we already know a natural law to the effect that "rubber becomes gooey when heated." For consider: suppose I place the ball on a hot plate and simultaneously wave my magic wand over it. After a while, it becomes gooey. Now, if natural laws are irrelevant to the question of causes, then it makes just as much sense to say that waving the wand was the cause, as it does to say the heat of the hot plate was the cause. In fact, it makes just as much sense to say that the flapping of a butterfly's wings was the cause, or the position of Jupiter in the sky. Without natural laws, we can have no conception of cause and effect.

I could continue to cite examples - breaking the glass with a brick (p.68: laws of force and fracture), the train pulling out of the station (p.95: laws of motion) - but I think you get the idea. In his latest post, Feser cautions against confusing illustrations of philosophical ideas with empirical evidence for them. The question remains: how can we know how causality works unless from our experience of actual causal sequences?

And if inertial motion is irrelevant to the First Way, then why does Michael Augros spend ten pages of this paper (PDF) dealing with the "problem" of inertial motion, and why is Feser himself writing a paper about it?

(One way to make the connection between laws and causes - if you'll forgive me getting technical for a bit - is via Hempel's deductive-nomological model of scientific explanation. On the DN model, a scientific explanation of a particular situation is a list of laws of nature, L1, L2, ... and a list of conditions, C1, C2, ... that guarantee the laws apply in this situation. Then the causes of the phenomenon can be identified as just the conditions, C1, C2, .... In the melting ball example, we would need (at least) a law of melting and a law of heat transfer. The conditions would include the contact between the ball and the hot plate, and the length of time they were in contact. Then we can clearly identify the hot plate as a cause of the ball's gooeyness - and likewise rule out the wand as a cause, as there is no natural law that would allow it to bring about the melting.

In this model the relationship between laws and causes is clear and explicit. This model has problems of its own, of course; it's just an example of the kind of account that Feser needs to give to make his position coherent.)

To be sure, Feser clearly realizes that there is a connection between our experience of the world and our concept of causality. In his first response, he wrote

Oerter ends his latest post with the remark that “It seems that physics is not, after all, irrelevant to metaphysics.”  Well, I don’t think I ever said that it is irrelevant.

And in this recent follow-up, he writes

Though metaphysics takes us well beyond the natural world, then, its concepts have a foundation in our empirical knowledge of that world -- to be sure, not necessarily in the knowledge of the specifics of the empirical world that natural science gives us, but in the knowledge of what must be true of any empirical world in general, which the philosophy of nature gives us.

 and

Now for the Aristotelian no less than for the empiricist, all of our concepts and all knowledge must ultimately derive from experience. 

In that post, he promises another response to my objections. Perhaps he will clarify how our concept of causation can be derived from experience, and yet the experience of quantum phenomena be irrelevant to that concept. 

Thirdly, Feser writes.

No, laws are not formal causes.

Good. Now will people please stop telling me that "the laws of quantum mechanics are the cause of electron transitions"? (This remark is directed at those commenters who made that claim, not at Dr. Feser.)

Finally, Feser writes

Now, along the same lines, we might say that the hydrogen atom also behaves as it does “spontaneously,” simply by virtue of having the substantial form it does.  Why do the electron transitions occur in just the pattern they do?  Because that’s the sort of thing that happens in anything having the substantial form of a hydrogen atom, just as gravitational attraction is the sort of thing that naturally happens in anything having a substantial form of the sort typical of material objects.  What is the efficient cause of this pattern?  The efficient cause is whatever brought a particular hydrogen atom into existence, just as the efficient cause of gravitational attraction is whatever brought a particular material object into existence.  That is one way, anyway, of giving an Aristotelian interpretation of QM phenomena of the sort cited by Oerter, and it is intended only as a sketch made for purposes of illustration rather than a completely worked out account.  But it shows how QM can be naturally fitted into the Aristotelian framework using concepts that already exist within the latter.

 This is actually very similar to what a physicist would say about the electron and its transitions. But it is a disaster for Feser's position. For, if spontaneous changes of state (with the emission of a photon) are just "the sort of thing that naturally happens" from time to time, then it is clearly not true that "Whatever changes is changed by something else." And so the First Way collapses.


I am not planning any more posts on The Last Superstition (which Prof. Feser will be glad to hear, I'm sure). Any further questions I have for him I'll post on the comments to his blog. Thanks to all of you who have taken part in the discussion, and biggest thanks to Prof. Feser for engaging my questions.
 

Moving Right Along...

In Dr. Feser's second response, he addresses the issue of local motion. It seems I need to read his other book, as well as a paper of his that hasn't even been published yet, to get the full story on local motion. Hmm. Since the one requires effort and the other requires violation of causality (physicist's version), it will be a while before I get to that.

In the book (p.102), Feser says local motion is irrelevant because Aquinas means change in general, and so "there would still be other kinds of motion so which Aquinas's argument would apply." As we saw earlier, though, this renders the First Way argument invalid. In the blog post, Feser seems to have abandoned that line. Maybe an implicit concession that it doesn't work?

Instead, he claims that inertial motion is not real change - "it involves no actualization of potential." (He's actually cagey in how he phrases this, writing, "... if such motion really is a state...." Of the five points he makes, though, this is the only one that explains how Aquinas's argument can be preserved, so I will take it as his (now) preferred solution.)  

Now, picture two objects, one in inertial motion toward the other. They get closer ... and closer ... but (according to Feser) there is no change occurring. This is a perfect example of the kind of absurdity you get when you don't allow physics to inform your metaphysics. It is obvious that at least one thing - the distance between the two objects - is changing. It is only by insisting on a rather bizarre definition of "change" that you can call this a case of no change.

A better way to go is to recognize that there are different kinds of change. Then we can decide what kinds of change need an explanation and what kinds do not. 

Newtonian physics has a simple and elegant solution. We distinguish between velocity (the rate of change of position) and acceleration (the rate of change of velocity). Then we declare that velocity doesn't need an explanation (it is something that is just in the nature of massive objects), but acceleration does. (The cause of an acceleration is what physicists call "force.") This is not just an advance in physics, it is also an advance in metaphysics. By making finer distinctions among the types of change that occur, we come to a better understanding of the meaning of "cause." Unfortunately for Feser and the First Way, with these new definitions it is no longer true that "Whatever changes is changed by something else."


As I said earlier, of course you can find definitions of "actuality", "potentiality," and "change" so that every change always has an external source. But if you find yourself insisting that even though those two objects are getting closer together, no change is occurring, then you ought to suspect that something is wrong with your definitions. 

ETA: I apologize that the middle part of this post is so poorly worded. In his second point under "Newton and local motion", Feser does say that there are two kinds of "change" (what he calls "motion"): the Newtonian kind and the AT actualization-of-potentials kind. Let's call the first n-change and the second at-change. Now he can proceed with the First Way:

1'. Whatever at-changes must be at-changed by something else.
2. The causal series can't go on to infinity.
3. Therefore, there must be a first at-changer.

(Note that the "first mover", which here becomes "first at-changer", is not yet the Unmoved Mover that Aquinas eventually reaches in his argument. All we can get from (1'.) and (2.) is that there is some first element in this particular causal series. There is no reason, as yet, to think that this must be "pure act".)

At this point, though, we have to allow that the whole series of at-changes might have been set off by an n-change. For instance, suppose our inertially moving object (A) and our stationary object (B) have a short-range force that acts between them, such that there is no force when the objects are far away, but a force begins to act when A gets close enough to B. When B feels this force, a series of at-changes begins: B breaks a laser beam that sets off a bomb, say.

So, even though the argument up to (3.) is logically sound, it doesn't get Feser what he needs: even though there is a first at-changer, the true initiating cause of the whole series is an n-change: something that doesn't count as a change at all in Feser's metaphysics!

Hope this makes things clearer....

Feser Responds

Dr. Feser has been kind enough to deem my critique of The Last Superstition worthy of a detailed response over on his blog. I want to say I'm genuinely grateful for this; it's not often I get the opportunity of interacting with the author of a book I'm reading in this direct way. (I also have to thank him for the photoshop job in his second response, which makes me look cooler than I've ever looked in my life.) While I'm sure that many of his accusations of conceptual confusion on my part are on target, I'm going to continue to push back, in the hopes of (a) clearing up some of my confusion, and (b) understanding his position better.

I also appreciate the great discussion that's going on in the comments - you folks post comments faster than I can respond to them, but other commenters are making many of the same responses that I would make, so all's well as far as I'm concerned.

My main point in this post was just that, whatever you think of universals such as numbers and propositions, colors at least are not mind-independent. In TLS, Feser made mind-independence part of his definition of realism:

The view that universals, numbers, and/or propositions exist objectively, apart from the human mind and distinct from any material or physical features of the world, is called realism.... (p.41)

And in his argument for realism, he emphasized that

When you and I entertain any concept - the concept of a dog, say, or of redness.... - we are each entertaining one and the same concept; it is not that you are entertaining your private concept of red and I am entertaining mine, with nothing in common between them. 

In his first response, though,  he seems to concede both these points. When he distinguishes between "RED" (the sensation or experience) and "red" (the physical properties that produce this sensation), he defines them as follows:

RED: the qualitative character of the color sensations had by a normal observer when he looks at fire engines, “Stop” signs, Superman’s cape, etc.

red: whatever set of physical properties it is in fire engines, “Stop” signs, Superman’s cape, etc. that causes normal observers to have RED sensations...

These definitions both refer to "a normal observer" and so are implicitly mind-dependent definitions.  (Unless Feser thinks we can define "normal observer" without reference to the physiological and psychological properties of human beings.) And he states

And even if it turns out that what you call RED and what I call RED are qualitatively different, that wouldn’t make any difference either.  For then it will still be the case that every instance of RED in my sense of “RED” is an instance of the same one universal, and every instance of RED in your, different sense of “RED” is an instance of a different universal, and so forth.

But in that case, we wouldn't be entertaining one and the same concept.

Feser calls his position "Scholastic realism,"

...on which universals exist either in the things which instantiate them or in intellects, but where the latter includes the divine intellect, in which they pre-exist as the archetypes according to which God creates.

That they can exist "in intellects" seems to allow for a certain amount of mind-dependence of universals - clearly a more nuanced view than what he presented in the book. I don't understand why this mind-dependence doesn't put him in the conceptualist camp, rather than the realist camp. But it seems that on the basic point - the mind-dependence of colors - we are in agreement. 

The First Mover

Now we're ready to tackle the First Mover Argument for the existence of God. It runs like this:

1. Whatever changes must be changed by something else. 
2. The causal series can't go on to infinity.
3. Therefore, there must be a first mover.
4. The first mover must itself be pure actuality: unmoved, unchanging, and unmovable.
5. Therefore the first mover is God.

That last step sounds a bit of a non sequitur, which Feser himself admits. He says that Aquinas devotes hundreds of pages to making the connection - I'll take his word on that. It's the rest of the argument I'm interested in. 

Recall that in the discussion of local motion, Feser abandoned (1.), and replaced it with something like "Some things that changed are changed by something else." This is fatal to his argument, though. Here's how he argues for (4.) (p. 95-96, for those of you following along at home):

Now, a first mover in such a series must be itself unmoved or unchanging; for if it was moving or changing - that is, going from potential to actual - then there would have to be something outside it actualizing its potential, in which case it wouldn't be the first mover.

This obviously relies on the idea that everything that changes is being changed by something external to it. If only some things that change require an external changer, then the argument is just a non sequitur. 

Let's back up, though, and look at his argument for (2.) Feser says that Aquinas distinguishes between two types of causal series: accidentally ordered series and essentially ordered series. In an accidentally ordered causal series, the cause could have happened some time in the past: it need not be present to produce the effect. His example is a father, who was the "cause" of his son. The father need not be still alive, though, for the son to go on existing. In an essentially ordered series, the cause must be there for the effect to occur. The example is of a hand that pushes a rock using  a stick. If the stick were not touching the rock, it would not be moving it, and if the hand were not pushing the stick, it wouldn't be moving the rock. Feser chases the chain of causation to deeper and deeper levels: the hand's motion depends on the firing of neurons, which depends on the biochemistry of the cell, which depends on the atomic structure of the molecules, which depends on the fundamental forces that govern particle interactions.

An accidentally ordered causal series could go on to infinity, says Feser. But not an essentially ordered series. (Thus, (2.) only applies to essentially ordered causal series.) The reason is that in an essentially ordered series, the later members only exist because the earlier ones do: the stick's push against the rock is only there because of the action of the hand. Feser says, "...it is only the first member which is in the strictest sense really doing or actualizing anything." He gives the example of a series of freight cars pulling out of a train station: the car you see is pulled by the one in front of it, and that one by the one in front of it, and so on. But they can't be all freight cars; somewhere up there there must be an engine car initiating the whole series.

What is needed is an appeal to something that does have the power of movement in itself, such as an engine car.

There are two problems with all this. First, the idea that causes can be arranged in nice ordered chains as envisioned by Feser just doesn't accord with what we know about the way the universe works.


The example of the train engine is what Dennett calls an "intuition pump." It's an example designed to make you think, "Of course there has to be a first member of the series." Here's a different example to pump your intuition a different direction: Think about two masses, A and B, in circular orbits around their common center of mass.

 The change in A's velocity is caused by B's gravity, and the change of B's velocity is caused by A's gravity. There's no need for one of these to be causally prior to the other.

Instead of nice ordered chains of causality, there are complex interconnecting webs of interactions. When all the causes are present at once, as they are in the situations Feser calls "essentially ordered chains,"  no one of them need be considered the "first."


 But even if we accept the idea that all causal chains are ordered, there is another problem from the physicist's point of view: everything in the world has the "power of movement in itself." Feser has slipped into talking about "movement," but recall that by this he really means "change." Changes, for the physicist, are the result of forces, and forces are part of the nature of those fundamental particles from which everything is made. It is the nature of massive particles to exert the gravitational force, of charged particles to exert the electromagnetic force, and so on. So any particle (or collection of particles) can be the "first mover" in the series.

(This post was written before I saw Feser's second response to my series. I will address his responses in a later post.)

PSR at Prosblogion

By curious coincidence, Joshua Rasmussen recently posted an argument about the Principle of Sufficient Reason over at Prosblogion, which includes a consideration of the quantum mechanical objection. Way to go, Josh!

Be sure to read the comment thread - lots of good stuff there.

Come On Baby, Do The Local Motion

The argument so far: Feser wants to establish that "Whatever changes is changed by something else," a crucial premise (as we will see later) for Aquinas's First Way of proving the existence of God. To do so, he has relied on the idea that when a change occurs there is always an explanation for why it occurred at that particular time. But the study of quantum systems gives us strong reason to doubt that there is always an explanation for why a change occurs at a particular time.

Now, there's another reason to doubt  "Whatever changes is changed by something else." It's Newton's First Law of Motion, aka the law of inertia: Whatever is in motion will stay in motion, unless acted on by an outside force. So here is another kind of change (a change of position) that doesn't require an outside changer.

(In fact, the First Way is traditionally known as the argument to a First Mover: "Whatever moves is moved by something else."  Feser says that "move," in the Aristotelian-Aquinean sense, is more properly translated as "change." I assume he is correct in this.)

Feser doesn't address the issue with quantum mechanics, but he does address the issue of inertia, or "local motion." He gives three reasons (p.102) inertia is irrelevant to Aquinas's argument.

1. Aquinas means change in general, and not just actual movement. The argument applies to changes of temperature, of state, etc. Thus, "...even if we were to grant that the local motion of an object needn't be accounted for by reference to something outside it, there would still be other kinds of motion to which Aquinas's argument would apply."

But to say this is to get rid of  "Whatever changes is changed by something else," and replace it with "Some things that are changed are changed by something else," or perhaps, "Every change of type X is caused by something else." Feser doesn't tell us what the replacement premise is. But, as we will see, none of these possible replacements is sufficient for the First Mover argument to go through.

2. "Second, whether or not an object's transition from place to place would itself require an explanation in terms of something outside it, its acquisition or loss of momentum would require such and explanation, and thus lead us once again to an Unmoved Mover."

Here the same objections apply as in (1.).

3. "Third, the operation of Newton's first law is itself something that needs to be explained...." If it is just in the nature of things that they continue to move, then we need an explanation of why they have that nature. This, Feser says, leads us to the Second Way.

But if it is just in the nature of things to change without any requirement of an external changer (as in local motion or quantum processes), then we have completely abandoned  the premise "Whatever changes is changed by something else." If all sorts of things can change without requiring an external changer, then there is no way to argue to a First Changer.

I'll show this in detail next time. But for now, notice that Feser's (3.) doesn't, in fact, show that the inertia problem is irrelevant to the First Way. (3.) may lead to some other argument for God, but it doesn't resolve the issue: that local motion is a change without any external changer.

Laws, Reasons, and Tigers Under My Desk

To recap: my claim is that the sort of spontaneous transitions that occur in quantum systems are a counterexample to the premise that "Whatever changes is changed by something else." In this post I want to consider some of the objections that were raised in the discussion on Dangerous Idea.

The laws of quantum mechanics are the cause of the change. This objection can be dismissed easily. The question is what causes the change to happen at the particular time it happens. QM is silent on this question.

Further, in most philosophical views of physical laws, the laws have no causal efficacy. For instance, we might think of laws as just descriptions of the way things actually behave. But a description of how something happens is not a cause of it happening. So, the moon's orbit around the earth isn't caused by the law of gravity. It's caused by the actual gravity of the actual earth.

Finally, even if we think of physical laws as having some sort of actual existence and causal efficacy, well, the laws of QM exist right at the moment the electron is excited, so by this view the electron should immediately decay. In Aristotelian terms, we are looking for the efficient cause: the thing that brings about the change at the instant it occurs. The laws of physics apply equally to all times; they can't be the reason something happens at some particular time.

(It seems to me that the laws of physics could be considered the formal cause in Aristotelian language. But Feser says that modern philosophers have abandoned formal (as well as final) causes. Does anyone know if laws can, or cannot, be considered formal causes?)

It's a metaphysical premise that can't be contradicted by any possible set of observations. Feser's argument was that, if nothing actualizes the potential, then there's no reason for it to happen at one time rather than another. If this is the basis of the metaphysics response, then you need to somehow justify the idea that there is always a reason for the change to happen when it does. To simply insist that there must be a reason is to beg the question. (It seems that there might be an implicit appeal to the Principle of Sufficient Reason here. Feser doesn't invoke it here, but later in the book he does mention it. But then you need a metaphysical defense of that principle.)

Alternatively, one could argue that the principle follows simply from the definitions of the terms "actuality," "potentiality," and "change." Now, I'm happy to admit that there are probably some definitions of those terms that allows one to deduce the principle from them. But then you are left with the question of whether those definitions have anything to do with the sort of changes we actually see in the world. Unless you're going to be content with a metaphysics that is completely divorced from the world of sense experience, you have to allow our observations to have some say about metaphysical principles.

Yours is just an argument from ignorance. Here the complaint goes something like this: "Just because quantum mechanics doesn't specify any cause for the decay to happen at that time, it doesn't follow that there is no cause. It may be that there are causes of which we know nothing, and which aren't part of the theory of quantum mechanics."

This is a valid point. Just because quantum mechanics (more precisely, relativistic quantum field theory) is the most amazingly well-tested, most accurate, most far-reaching description of the universe that we have ever produced, we can't just conclude that it's the end of the story. Maybe quantum mechanics is incomplete - maybe there is some further, more precise, theory that will tell us about the causes of electron transitions and radioactive decay. (Or even, though such a theory might not be attainable, that there nevertheless are such causes.)

This one requires a rather lengthy response. This very point was raised in a famous paper by Einstein, Podolsky, and Rosen, who argued in 1935 that quantum mechanics must be incomplete. Discussion of this important claim continues to this very day. An major advance came in 1964, when John Bell showed that (under a very general set of assumptions) any attempt to "complete" quantum mechanics would end up making predictions that differed from those of QM. This led to a series of experiments designed to look for such differences. The upshot: quantum mechanics has come out the winner in every test to date.

This is a long, complex, and on-going discussion. Fortunately, we can bypass the details. We don't need to make all of Bell's assumptions to see that any additional "causes" added to quantum mechanics will result in violations of quantum mechanical predictions.

Let's suppose that there is some physical property - something not included in the quantum mechanical description - that determines for each atom exactly when the electron will decay. Call it property A. Since property A is a physical property, it must have some physical effect. If it has some physical effect, then it must be possible to separate out systems with one value of property A from systems with some other value. That is, we can use property A as a filter. (I'm borrowing this filter idea from the brilliant Von Neumann.)

Applying this filter, we separate out a subset from our original set of identically prepared atoms. This subset, having a physical difference from the original set, will have a measurably different set of physical properties. (If it doesn't, then there's no point in considering property A to be a real, physical property. If this "property" makes no measurable difference in the world, in what sense is it a real physical property?) Thus, this subset will violate the rules of quantum mechanics.

Now, I put it to you that the 100-year history of successful predictions of quantum mechanics strongly suggests that there are no such additional physical properties. To call this an "argument from ignorance" is just absurd. It's an argument from "we've looked really really hard for this and haven't found anything like it ever." (Is there a tiger under my desk? "No, I just looked and didn't see one." "But that's an argument from ignorance!")

So, quantum mechanical processes give us strong reason to doubt the premise that "Whatever changes is changed by something else."

Physics > Metaphysics

Last time, we saw that in trying to establish the principle "Whatever changes is changed by something else," Feser argued that a potentiality can't be actualized by nothing, because then there would be no way of explaining when the change occurred.

This seems reasonable: the ball melts when it does because of the heat that has been applied to it, the window breaks when it does because the baseball hit it at that moment, and so forth.

But, over the last hundred years, physicists have discovered systems that change from one state to another without any apparent physical "trigger." These systems are described by quantum mechanics.

The simplest such system is the hydrogen atom. It's just an electron bound to a proton. Two particles - that's about as simple as you can get. According to QM, the electron can occupy one of a discrete set of energy levels. The electron can be excited to a higher energy level by absorbing a photon.

When the electron drops from a higher energy level to a lower level, it emits a photon: a quantum of light.



Quantum mechanics describes this process beautifully, but it only predicts the average time the electron will stay in the higher energy level. It doesn't give any clue as to the specific time the electron will drop to the lower level. More precisely, the transition rate (the probability of a transition per unit time) is constant: it doesn't matter how long it has been since the atom was excited, the transition rate stays the same.

Compare this to human lifetimes. There is some average human lifetime. But the probability of death ("transition to the lower state" - ha ha) depends on how long the person has been alive. A 90 year old has a much higher probability of dying in the next year than does a 30 year old.

In contrast, the electron has the same decay rate after one year as after one microsecond.

When you first encounter this, you can't quite wrap your brain around it. Surely there must be some internal mechanism, some kind of clock, that ticks along and finally "goes off," causing the transition!

But no such mechanism has ever been found. QM has had an unexcelled record of accurate predictions, without any need for such a mechanism. Further, we have good reason to suspect that, if there were such a mechanism, then QM would not be accurate in its predictions. (I'll come back to this point in a later post.) So, the absence of violations of QM is evidence that Feser's expectation - that there is always a reason for a change to happen when it does - is just wrong.

Feser seems to have missed out on the last hundred years of physics: he shows no hint that there might be a problem here. (His index includes "quantum mechanics" exactly once, in an unrelated context.) It seems that physics is not, after all, irrelevant to metaphysics.

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.

Universal Truth

I'm going to try to argue that The Last Superstition fails to make the case for Feser's preferred metaphysics. I want to be clear that I'm only attempting to address Feser's argument, as presented in this book. There might be a much more effective case to be made, and maybe it can be found in Aquinas, or in Feser's other books, none of which I've read. But he presents his case in this book as an (irrefutable!) logical argument for God, so that's how I'll treat it.

One of the first things Feser tackles is the problem of universals. This philosophical problem has a 2000 year history, and is still a matter of debate today. Yet Feser claims that conceptualism and nominalism, the major alternatives to  Feser's preferred realism, are demonstrably false. I guess none of those other philosophers were smart enough to see that the problem had already been solved.

As examples of universal, Feser lists "triangularity," "humanness," and "redness." And by realism about them, he means that they "exist objectively, apart from the human mind and distinct from any material or physical features of the world."

Now, redness is an interesting choice. We now know a lot more about color perception than Aristotle did. What we know as colors are the result of a complex interaction among the light source, the surface of the colored object, the physiology of the eye, and the processing that goes on in the brain.

Start with an obvious point: "red" is an English word. We can translate it into other languages - but can we be sure that the extent of "rot" in German (for instance) coincides with "red" in English? Maybe, and maybe not. But some languages don't have a word that even vaguely resembles "red." The Jale of New Guinea have only two color terms: roughly, "brilliant" and "dull." The Tiv of Nigeria have three color terms:

 ii, which encompasses all greens, some blues, and some greys; pupu, which encompasses very light blues, light greys, and white; and nyian, which encompasses red, some browns, orange and yellow.

When someone says "The apple is red (nyian)" in Tiv, they are saying something very different than I am when I say that sentence. So it is clear that color is a culturally dependent quantity.

Even within our own culture, people can differ about what a term means. "That's not red, that's maroon!" If twenty people looked at this chart and picked out the colors they would label "red," there might not be two lists that agree. And it's not just a matter of definition: people's perceptions of color can differ dramatically. This is most obvious in color blindness, but here's a personal example that doesn't involve color blindness. When my wife and I were house hunting, we discussed one house that had (my wife thought) beautiful green marble counter-tops in the kitchen. "They weren't green, they were black!" I exclaimed. And it wasn't just a matter of lighting or recollection: we now live in that house, and my wife maintains that we have green counter-tops (with black flecks), while I am sure that they are black (with some green in them).

But if you really want proof that colors are not mind-independent, just look at the following image:


Do you see the green and blue spirals? So do I: but there aren't any green and blue spirals. Those spirals are exactly the same color. (r = 0, g = 255, b = 150) That is to say, in every objective, measurable sense, they are the same. Yet our minds interpret them as different colors.

Imagine that an extraterrestrial lands on Earth. Its physiology is completely different from ours. Maybe it doesn't even perceive light: it gets around by some sort of sonar. How would you explain why an apple and a fire engine are both red? How would you explain why two of those spirals are green and the other two blue?

 It is clear, then, that colors are not mind-independent. But that at least leaves open the possibility that other things that seem obviously mind-independent are, in fact, mind-dependent.