Dialogues on Psychophysical Harmony, Part 2

A posteriori physicalism, and the (simple) evolutionary objection

Setting: A and T have reconvened for brunch.

…

T: So, are you ready to find out why theism is a much better explanation of psychophysical harmony than naturalism?

A: No.

T: You wanted to find out yesterday. Now you don’t? What gives?

A: Well, having thought about it some more, I’ve figured out that your starting assumption is false: psychophysical harmony need not be ridiculously surprising on naturalism, contrary to what you said.

T: But you agreed with that claim before.  

A: And I’ve changed my mind. Can’t I change my mind? What are you, the thought police?

T: I’m not, and you can, but what made you change your thinking?

A: This. And brace yourself. You’re about to have your mind b-lown!

T: I’m ready.

A: Last time we met, you argued the following, didn’t you: there are psychophysical laws; these laws give rise to psychophysical harmony; and this fact is incredibly surprising on naturalism.

T: I did indeed.

A: Well, you were right about the first parts: there are psychophysical laws and they do give rise to psychophysical harmony. But the last part is an unjustified assumption. Psychophysical harmony need not be incredibly surprising on naturalism.

T: Why not?

A: I’ll tell you why not: yesterday, you were saying that it was possible for the psycho—

T: Well—

A: Can I finish?

T: Yes, yes, of course. Sorry – go ahead.

A: Yesterday, you said that it was possible for the psychophysical laws to have been combined in about a trillion-million-gazillion different ways. But why would the naturalist accept that? Why couldn’t the naturalist just say that there’s only one way the psychophysical laws could’ve been: the way they actually are. If the naturalist says that, then it’s totally unsurprising that the psychophysical laws are the particular way they are. Why? Because they couldn’t possibly have differed.

T: Apologies for the interruption. But what I was going to say just then was that I never made it a part of the argument that the psychophysical laws could actually have been different. That wasn’t something I said. All I said was that conceivably they could have been different than they are. That is, I said that we can coherently imagine them being different. I said nothing about whether alternative psychophysical laws were actually possible.

A: Are you sure?  

T: Yes. All I said was that we can conceive of the psychophysical laws having been different.

A: Ok, but what difference does that make?

T: All the difference in the world, my friend.

A: How so?

T: Here, let me illustrate: Imagine that in a thirty years’ time, scientists send robots to explore the surfaces of planets beyond our solar system. On one of them, McLuvin’ 16-B, they discover a new type of crystal. When the crystal is split in two, the inner surface spells the following English sentence, written in crystal: “Dear NASA, it’s been thirty years and people are still talking about “rizz”. Please make them stop. Yours sincerely, for I cannot lie, יהוה‎.” On neighbouring planets, the robot discovers thousands of other crystals of the same family. In all of them, the same exact message is written.

A: Ok…

T: At first, the scientists assume the crystals were engineered by intelligent aliens playing a practical joke on NASA.

A: Seems like something they’d do.

T: But later, the scientists discover, through some Extremely Hardcore Science, that the development of these specific crystals containing these specific messages is built into the laws of physics – meaning aliens couldn’t have been responsible for them, because even technologically advanced aliens couldn’t change the laws of physics.

A: Right.  

T: My question for you: if this actually were to happen, if NASA scientists really did discover these crystals growing on faraway planets, and if they really did go on to discover that the development of these crystalline patterns was built into the laws of physics, should naturalists be surprised by it?

A: You’re trying to entrap me.

T: I am. But role with me here: give the answer that seems right to you.

A: Ok; yes, if this were to happen, it seems like naturalists ought to be surprised. They should probably also give up naturalism and become theists or simulation theorists.

T: I agree. It seems obvious that if these crystals were actually discovered, naturalists should be surprised by it.

A: So… what’s the trap I’m supposed to have walked into?  

T: It’s this: just before, you said that if we suppose that a given law of nature is necessary, then nothing that results from it can be surprising, no matter how uncanny or strange it is, correct?

A: Yeah, that’s what I said.

T: Alrighty then. Now imagine this scenario: One of the NASA scientists – call her Gretel – upon learning about the crystals and the message they contain, says: “Pfft, this isn’t evidence for God! No way! Sure, my colleagues discovered crystals apparently containing a direct message from the God of Abraham. And sure, we now know, having discovered it to be the case through some Extremely Hardcore Science, that the development of those crystals with these patterns is a direct outgrowth of the laws of physics. But I believe that the laws of physics and everything that results from them are necessary and inevitable – according to me, and my favourite philosophical theory, the laws couldn’t possibly have been any different. Therefore, the ‘message’ in the crystals doesn’t move me towards theism in the slightest.” Question: Would you be satisfied by Gretel’s response?

A: No.

T: Why not?

A: I’m not sure exactly what’s wrong with Gretel’s reasoning, but the conclusion she came to is clearly false: it would be crazy to think that if we really found a message like that, we would have no more evidence for God’s existence than we had before. Denying that we’d have evidence for God in that scenario would be dogmatic and unreasonable. Merely asserting that the laws of physics are necessary doesn’t in any way predict that the laws of physics would produce this spooky religious message.

T: Swish – nailed it.

A: I did?

T: You did.

A: Explain.

T: Well, like you said, merely theorizing that the laws of physics are necessary doesn’t by itself predict the datum in question. That is, it doesn’t by itself predict the message. The scientists have discovered something very surprising: crystals, arising from the fundamental laws of physics, that contain the same written message from God. This fact is surprising. It calls out for explanation. What it specifically calls for is a hypothesis that will predict the data in question, something that will make the message in the crystals less surprising. But theorizing – in the abstract – that the laws of physics which produced them are necessary doesn’t do that. It doesn’t predict the data at all.

A: Why not?

T: Because the hypothesis that the laws of physics are necessary doesn’t give rise to the specific prediction that there would be these crystals. If you told a genius who knew nothing about physics that the laws of physics are necessary, he would have no way of deducing – from what you’ve said – what the laws of physics actually were. All you’ve given him is a broad claim about the laws of physics: that claim doesn’t predict anything about what the laws of physics will actually turn out to be.

A: I see. But couldn’t you just modify the theory that “the laws of physics are necessary” so it would predict the message in the crystals? Couldn’t you just make the message in the crystals part of the theory? As in, could you just modify the theory so it said: “The laws of physics are necessary and they give rise to crystals containing an apparent message from God”?

T: You could, and if you did, your theory would successfully predict the data…

A: I sense a ‘but’ coming…

T: …but, modifying the theory in that way would make it vanishingly improbable.

A: Why?

T: Imagine we’re playing poker and I keep winning. More precisely, every time I deal myself a new hand, I wind up with a royal flush in spades. If that were to happen, would you suspect me of cheating?

A: I would.

T: But then imagine if I said, in response: “A, I’m not cheating. Everything that happens in the universe is necessary and inevitable – including the fact that I keep dealing myself a royal flush in spades!” Would you be convinced?

A: No.

T: Why not?

A: For the reason we gave earlier about the scenario with the crystals. Just saying that a really surprising event was inevitable doesn’t make it any less surprising.

T: But suppose I replied to that with the following: “Ok, ok. Hear me out here: my theory for why I keep dealing myself a royal flush in spades isn’t just that everything that happens in the universe is inevitable. It’s that everything that happens in the universe is inevitable and that, as a result, I am destined to keep getting royal flushes.” Would you believe me then?

A: No.

T: Why not?

A: Because… because the odds of that are really low.

T: Exactly. The prior probability – the probability we give to whether something is true before we know whether it is true – of me dealing myself a royal flush in spades every single round of the game is ridiculously low. So when we conjoin the claim that “I will deal myself a royal flush in spades in every round without cheating” to the claim that “everything that happens is inevitable”, the resulting claim retains this ridiculously low prior probability. This drags the whole theory down with it, making it ridiculously improbable.

A: So how does this relate to psychophysical harmony?

T: Before, you were suggesting that naturalists can explain psychophysical harmony by positing that the psychophysical laws are necessary, and that they couldn’t possibly have been any different. But this move doesn’t work: Merely positing that the psychophysical laws are necessary doesn’t predict that they’d be harmonious. But to make psychophysical harmony less surprising, which is what we need to do, we need a theory that predicts it: merely positing that the psychophysical laws are necessary doesn’t do that. You could try to correct for this by changing your theory from “The psychophysical laws are necessary” to “The psychophysical laws are necessary and they’re harmonious”. This would successfully predict psychophysical harmony, trivially, because psychophysical harmony has just been baked into the theory. But changing the theory in this way comes at a proportional cost to its prior probability. And because the prior probability of there being harmonious psychophysical laws is ridiculously low, this makes the probability of the theory ridiculously low. In other words, positing that “The psychophysical laws are necessary and that they’re also harmonious” would successfully predict the data, but would sink the probability of the theory.

A: I see. It’s possible you’ve sunk my battleship…

T: So, are we closer to agreeing now? That psychophysical harmony is ridiculously surprising on naturalism?

A: No, we most certainly don’t!

T: We don’t?

A: We don’t.

T: Why not?

A: Because, dear T, I have another objection, another reason why psychophysical harmony is unsurprising on naturalism.

T: Let’s hear it.

A: Prepare, again, for a mental explosion.

T: (prepares, again, for massive disappointment)

A: Are you ready?

T: As I’ll ever be.

A: Two words: Natural. Selection.

T: What?

A: Evolution. Ever heard of it?

T: Yes, but what about it?

A: Isn’t it obvious? Psychophysical harmony is explained by evolution! If an animal lacked psychophysical harmony, it would die. If all a zebra could see was the colour black, it wouldn’t be able to see where it was going. It would run away from food and into tigers. From an evolutionary standpoint, psychophysical harmony would be highly adaptive, whereas disharmony would be highly maladaptive, at least if you’re a conscious creature. So, like all highly adaptive traits, psychophysical harmony would be selected for by evolution. There’s no puzzle here at all.

T: Yes there is.

A: No there isn’t.

T: There is.

A: Isn’t.

T: Is.

A: Isn’t.

T: No, there is. Here’s why: Imagine a zebra running from a lion.

A: Ok…

T: It’s running, it’s running, it’s getting away, and… it stops. Its path is blocked by an massive stone. There’s no way around the stone. The only way for the zebra to escape the lion would be to turn into a ghost, pass through the obstacle, and materialize on the other end. Do you agree that would be an adaptive feature for a zebra in this situation to have?

A: Yes, but turning into a ghost is physically impossible for an animal. The laws of physics don’t allow for it.

T: Exactly. The same is true of other potentially adaptive abilities, like flying in a way that defies gravity, or fleeing predators faster than the speed of light.

A: True.

T: Well, this rule carries over to the psychophysical realm. If the psychophysical laws didn’t allow for psychophysical harmony, it could never have been selected for. Conceivably, there could’ve been zillions of ways that the psychophysical laws could have been such that they would never have allowed psychophysical harmony to be selected for.

A: So you’re saying… the evolution objection doesn’t really address the problem.

T: Exactly.

A: (looks mournful, then immediately perks up) Wait, but you haven’t heard my third objection!

T: There’s more?

A: There is.

T: Let’s hear it then!

A: No.

T: What?

A: No. I’ll tell you another day – I have a date!

T: No you don’t.

A: No, I don’t. But I am busy – I’ll have to love you and leave you.

T: Ok. Later alligator.

A: In a while, crocodile.

T: In a week, freak.

[To be continued…]

[For more on the argument from psychophysical harmony, see Cutter and Crummett’s “Psychophysical Harmony: A New Argument for Theism”: https://philarchive.org/archive/CUTPHA Views expressed here do not necessarily represent the views of the argument’s inventors.]