A bad response to a good argument from design

I've been talking to a friend recently about the Fine-Tuning Argument for the existence of God and about a response to it called The Anthropic Principle, which he finds convincing and I do not. In this post I'll lay out briefly what the Fine Tuning Argument is, how the Anthropic Principle is used to respond to it, and why I think it's a bad response.

The Fine-Tuning Argument

This is an argument from design – a teleological argument. Based on our current understanding of fundamental physics, it seems that the fundamental constants of the physical universe both 1) don't have to be as they are, and 2) would not support life if they were even slightly different. A quotation from this Guardian review of a book about this (Just Six Numbers by Martin Rees) describes it somewhat:

One can marvel, almost indefinitely, at the balance between the nuclear forces and the astoundingly feeble but ultimately inexorable power of gravity, giving us N, a huge number involving 36 zeroes, and nod gratefully each time one is told that were gravity not almost exactly 10³⁶ times weaker then we wouldn't be here. One can gasp at the implications of the density parameter Ω (omega), which one second after the big bang could not have varied from unity by more than one part in a million billion or the universe would not still be expanding, 13.7bn years on.

...

All six values featured in this book permit something significant to happen, and to go on happening. Take for instance Q, the one part in 100,000 ratio between the rest mass energy of matter and the force of gravity. Were this ratio a lot smaller, gas would never condense into galaxies. Were it only a bit smaller, star formation would be slow and the raw material for future planets would not survive to form planetary systems. Were it much bigger, stars would collapse swiftly into black holes and the surviving gas would blister the universe with gamma rays.

The gist is that slightly different values for these constants would lead to a universe incompatible not just with the kind of life we find on earth, but any possible life. The argument then goes that it's much, much more likely that our universe was created with these parameters fine-tuned to allow for life than that the single universe that exists just happens, by random chance, to have these parameters.

Some Decent Responses

Here, briefly, are some decent responses to this argument. I don't think they all work, but they're not terrible.

1. The argument is based on our current understanding of physics, which may change, so we shouldn't put too much stock into it and create yet another "God of the gaps" argument. This is true, but with everything we have to use the best knowledge we have now. Plus our understanding on this has been the same for decades and there doesn't seem to be any sign of that changing.
2. The universe isn't actually fine tuned. In my experience, that argument tends to approach the issue from a different angle: from the inhospitality of most of the universe to life, even most of our planet to intelligent life. But that doesn't directly address the argument, and leaves open the possibilities both that these are necessary side effects of this kind of design, and that such things might not be wasteful in the cosmic perspective of a bountiful God.
3. The universe doesn't need to be fine-tuned because life is more variable and resilient than we think, especially if we think beyond carbon-based life. This doesn't work for some of the scenarios considered by the argument, such as no stars forming or the universe collapsing back in on itself. But it might expand the range of possible universes more than some think.
4. Even by the arguments' claims we just don't know enough about how those constants might vary together. A lot of what I've read on it seems to talk about varying one constant while keeping the others...constant. That's likely because that's the easiest way for us to reason about it. It's much harder for us to know what'd happen if we varied 2 or 3 or all of them at once. Maybe there are many combinations compatible with life.
5. There are many actual universes – maybe infinitely many, maybe as many as there possibly could be – and we just happen to be in the one (or one of the ones) that supports life. That makes sense to me as a response, but I don't see why believing that is preferable to believing that God chose to make a habitable universe.

Those are some responses that I think are decent and that might even work to reasonably dull the blow of the fine tuning argument. However, for some reason, there's another argument that seems to be favoured by many atheists, an argument that I think doesn't work at all.

The Anthropic Argument

Despite reading and talking a fair about it, I still find the Anthropic Principle difficult to formulate as a response to the Fine Tuning Argument. But I'll give it a try here. Note that I'm intentionally trying to formulate it myself rather than to just copy-paste what somebody else said.

The response typically uses what's called the Weak Anthropic Principle (the strong one is kinda silly), which says something like this:

We can only observe universes that are hospitable to human life.

And that's obvious since we can only observe universes from inside. This isn't like us observing the moon or other planets from our comfy Earth.

But then what does that have to do with the fine-tuning argument? The response seems, glibly, that we shouldn't question the origins of the universe because if we weren't around we wouldn't be able to question it. But that both doesn't follow and is disturbingly incurious. Fortunately that's not the sense in which people intend the response.

One way I can see the response working is to pair it with a many worlds view like the number 5 in the list above – i.e. that there are many, maybe infinitely many, universes with different combinations of the physical constants. Let's consider a version with what I'll call exhaustively many universes – i.e. a universe for every possible configuration of the fundamental constants. Then the Anthropic Principle is merely pointing out that, of all the existing universes, we just happen to be in one that supports life. It's improbable that a universe chosen at random will have life, but given exhaustively many universes, every universe observed by life will be one that supports life.

Can this view work without there being, actually, exhaustively many universes? That is, can this work with merely possible universes? Proponents of this view seem to think so, but I don't see how. The difference between the two can be seen by looking at the two relevant probabilities we have on the view of exhaustively many universes:

1. The probability that an external observer randomly chooses a universe with parameters supporting life is nearly zero.
2. The probability that an internal observer randomly chooses a universe with parameters supporting life is 1.

Which one is ours if we have a single universe the fundamental constants of which are randomly chosen? The answer is obviously (1). The randomness we care about here is a random sample from the set of all possible combinations of the fundamental constants. Internal, living observers have nothing to do with it.

Put another way, the ability of an internal observer to observe the universe is obviously irrelevant at the time the universe's constants are set, and that time, not 13.7 billion years later, is the time we're interested in.

So, assuming that the universe's constants were randomly chosen, we have a very, very small chance that the one universe that exists would support life. And so these constants being determined by some non-random process – such as the deliberate choice of an intelligent being – is much, much more likely than them being due to random chance.

Two analogies

When talking about this, people often reason with analogies. I've avoided that so far here because, in my conversations, I've found that they obscure at least as much as they clarify.

But because of how common they are I'll close with two of them. The first is somewhat pro-Anthropic, and the second is common on the anti-Anthrpic side.

The first is from Douglas Adams:

Imagine a puddle waking up one morning and thinking, "This is an interesting world I find myself in, an interesting hole I find myself in, fits me rather neatly, doesn't it? In fact, it fits me staggeringly well, must have been made to have me in it!"

This assumes that life is very, very malleable and capable of developing in many, many kinds of universes, so it's more an argument that fine tuning isn't needed (number 3 in my list of decent responses above) than a version of the Anthropic Argument.

The second goes like this.

Suppose you were sentenced to death by firing squad for your puzzling view that the Anthropic Principle is a good response to the Fine Tuning Argument. The dictator so sentencing you has assembled a competent firing squad of some of the best marksmen. They're well-rested, their weapons are working well, and the execution arena is perfectly suited to killing you. You're tied down so you can't move, and close your eyes to make the process easier for yourself. The signal is given, they all fire, you hear the BANGs of their guns, and, lo! You're not dead!

You open your eyes in surprise, happy to smell the stench of the gunpowder, and see bewilderment on the faces of the crowd gathered for your execution, a bewilderment that you imagine is also on your face. Would it be unreasonable for you to think that maybe the marksmen chose not to kill you? Wouldn't it be silly for you to think that they all intended to kill you, their weapons were functioning perfectly, but, completely by chance, they all missed?