In a piece on the Scientific American guest blog, the day before mine, Sean Carroll made an interesting argument:
Claims that some form of consciousness persists after our bodies die and decay into their constituent atoms face one huge, insuperable obstacle: the laws of physics underlying everyday life are completely understood, and there’s no way within those laws to allow for the information stored in our brains to persist after we die.
He appeals to the Dirac equation:
How is the spirit energy supposed to interact with us? Here is the equation that tells us how electrons behave in the everyday world:
Don’t worry about the details; it’s the fact that the equation exists that matters, not its particular form. It’s the Dirac equation — the two terms on the left are roughly the velocity of the electron and its inertia — coupled to electromagnetism and gravity, the two terms on the right.
As far as every experiment ever done is concerned, this equation is the correct description of how electrons behave at everyday energies. It’s not a complete description; we haven’t included the weak nuclear force, or couplings to hypothetical particles like the Higgs boson. But that’s okay, since those are only important at high energies and/or short distances, very far from the regime of relevance to the human brain.
If you believe in an immaterial soul that interacts with our bodies, you need to believe that this equation is not right, even at everyday energies.
This is quite right, of course. A similar point can be made against telepathy, clairvoyance, and other “paraphysical” phenomena. If these are supposed to work like physical energies, they cannot exist, because we know enough about the physical world now to rule them out. New Ageism is baloney, if you hadn’t figured it out, and chi is the invention of modern exponents of a “medicine” that is leading to the extinction of many fine animals. Also, dualism is in trouble in philosophy of mind for these very reasons.
However, my friend Massimo Pigliucci picked up on this and tweeted it with the slug “Why there is no need to be agnostic about life after death.” This got me thinking: this argument is fine so long as it stops with the conclusion that science gives us no reason to think there is a soul that persists after physical death. But if you go further, and insist that this means we should rule out that possibility because it doesn’t cohere with the Dirac Equation (or the rest of known physics), well then that is question begging, and it goes to the heart of the New Atheist movement, I think. Let me explain.
Often, those in that movement, many of whom are friends of mine even though we dispute vociferously about meta-questions like this one, insist that all knowledge is scientific (Larry Moran is one of those), or at least, knowledge based on techniques that are refined and extended in science (which is of course my argument in the piece that followed Carroll’s). But those who think there is a soul, or the mind exists independently of the physical world, do not make this presumption. They hold that one can believe in the physical sciences but also believe in the nonphysical. This is what accommodationists like me do not rule out (but do not necessarily believe, either – I’m as physicalist as they come; it’s just that I don’t automatically think those who aren’t are fools or incompetent reasoners).
In order to eliminate souls because they are not physical things, which is what rejecting agnosticism about souls would involve, one needs to have a further claim: any belief that is not acquired through scientific means is untenable. Let us call this claim U. Now, let us ask this question: how do we acquire the belief that U? Is it based on scientific reasoning? How could it be? It is instead the precondition for doing science. This is exactly the point made about the logical positivists by Popper among others: If it is a true view then it is self-defeating.
Logical positivism held that any thesis that was not based on observation sentences and their formal consequences was metaphysics, and metaphysics was inherently nonsensical. Consider the claim metaphysics is inherently nonsensical. On what observation sentences is that based? None, therefore (by their own definition) it is nonsensical. But it is the foundational claim of logical positivism, ergo logical positivism is self-defeating.
The claim made here is that U is implied by science, and yet, it cannot be, for no amount of scientific reasoning will establish U over not-U. It is itself a belief that is not scientific. If you say that we should prefer U because past observation has shown it to be fruitful or successful, then in order to make the claim scientific you need a missing premise – that what we have observed to be successful is what should be preferred. Call this U‘. Is U‘ itself a scientific claim? Where in the Dirac Equation is that shown? And so on.
At the very least you need to adopt a philosophical (or, if you prefer the older terminology, “metaphysical”) position in order to assert that only beliefs that have been established by scientific means should be adopted. It happens I agree with that belief, but I recognise it is not itself a scientific belief, so I have an inconsistency in my belief set (I get around that by taking some beliefs to be higher order meta-beliefs; it gets messy). Someone who comes along and says that not-U‘ is to be preferred, that beliefs need not all be scientific, is not being irrational, although that raises problems for them they must subsequently deal with (like, “how do you know these beliefs then?”).
So what does all this have to do with agnosticism about souls? If one accepts that some rational thinkers might hold beliefs that are not defeasible by the Dirac Equation, et al., so long as they do not flatly contradict the best physics we have, what doxastic attitude should one have towards those beliefs? Should one just assert as a truth that is ungrounded and unsupportable except circularly, that one should reject nonscience? Should one say that this belief is acceptable? That any belief that doesn’t contradict science outright is possibly true?
I have beliefs about the soul that treat it as unlikely and probably false. I most certainly do not think the soul is something that can be physical and survive death (information always has a substrate and an energetic cost, and so it cannot exist without both). But do I therefore think the concept of soul is incoherent? I can’t see how I might establish that. As a question of knowledge, I know the soul is not a natural (that is, physical) thing, but I do not know, and neither does anyone else, that the soul does not exist. The only rational solution is to be agnostic about it until some evidence comes in that resolves the question, and since evidence is something that happens in a scientific manner, through observation and measurement, any existing thing that is neither is beyond the competence of science to determine.
So there remains reason to be agnostic about the soul (mutatis mutandis, God). Sure, some kinds of souls (Aristotle’s motivating forces, for example) are ruled out of contention by the Dirac Equation. But not all are. So agnosticism is the only rational position to hold here, unless you can accept there are nonscientific (philosophical) beliefs that are justified, in which case the argument is self-defeating.
Late note: And as if to obligingly demonstrate the logical positivist view, PZ Myers posts this. Thanks, Paul.