The fine tuning argument is (still) a failure

Thanks to Hello Orange for joining. Here, I will firstly explain how a fine tuning argument works. Then I will show it doesn’t. Framing the Fine tuning argument The Cosmological data suggests that a universe with any of its initial conditions or parameters (like the cosmological constant, the strength of the gravitational force, etc. etc.) were ever so slightly different, there would be no opportunity for intelligent life to exist - the universe would collapse back in on itself, there would never be any matter, etc. etc. In short, the universe seems 'fine tuned' for intelligent life. This can be used as an argument for theism. If (as theism says), the universe is the product of God's creative agency, then that the universe has intelligent life like us is unsurprising, for this is what God wants.[1] Yet, on Atheism, there is no such expectation, and if life-permitting universes only occur with finely tuned parameters, it is awfully surprising one just happened to occur. A Bayesian gloss (after Collins 2009):[2] P(LPU|T & k') >> P(LPU|ASU & k') LPU: Life permitting universe T: Theism ASU: Atheistic single universe[3] k': our background knowledge, subtracting (inter alia) knowledge of our existence or this universe existing.[4] So if, as the fine tuning data suggests, a Life Permitting Universe is ultra rare in the space of possible universes, then P(LPU|ASU&k’) is ultra low. Providing P(LPU|T&k’) is not ultra low, we have confirmation of Theism over Atheism, and the fine tuning argument is successful. So why is it a failure? Possibilia This argument implies the universe ‘could have been different’ with respect to its fundamental values, parameters, etc. On the face of it, this talk is tricky – we don’t know what the ‘universe generator’, if any, is. So there is no guarantee that the universe on Atheism would be formed by some random setting of all the separate dials. Yet if we do not know the process, how can we say a particular result is improbable? It seems the best hope for the Fine-tuning argument is to apply indifference to all epistemic possibilities. Given we have no idea how a universe (or laws of physics) would be formed, on Atheism, our best estimate is to assume all conceivable ways the universe could conceivably turn out is equiprobable: so the probability of the gravitational constant landing between x and x+c is the same as x and x-c. Given the ‘life permitting range’ of all sorts of constants looks very small indeed, we should still say P(LPU|ASU&k’) is ultra low.[5] In the field of all epistemic possibilities, life permitting universes are rare. Modal explosion And here begin the problems. Once we do this, P(LPU|ASU&k’) is not ultra low, but rather unknown: because the value of P(LPU|ASU&k’) now depends on a vast field of possibilities, most of which we have no means to evaluate. Our best physics allows us to predict what happens if we tweak a given parameter slightly, but does not predict what would happen in a universe with all the parameters changed by millions of orders of magnitude. So although life permitting universes might be rare in our locality of the universe-space, we do not know whether they are rare generally. It gets worse: we don’t just need to evaluate worlds with radically different values – we need to consider possibilities of physics entirely alien to our own. Two examples. Alien physics 1: There are a million physical parameters. Only in the case where each of these are exactly 1 is the universe life permitting. Alien physics 2: There are four physical parameters. Any combination of values for these parameters results in a life permitting universe. Both of these are possible - it is (remotely) possible that this universe really has alien physics 1 or 2 – our best science is possibly wrong. Of course, we can dream up conceivable alien physics ad infinitum. We have no way of estimating, over the space of all possible laws of physics, how likely a life permitting universes will be formed ‘by chance’. We therefore have no idea whether it is more likely to have a life permitting universe on Theism than on Atheism. Therefore there is no confirmation, and the fine tuning argument is a failure. Objections and replies One may say that alien physics and wild values are actually impossible, and so shouldn’t be considered. Yet why believe that? Why must the values necessarily be fairly close to the values of this universe? Why are these particular laws of physics necessary? If we’re willing to say that, why not go further and say the values of this universe are necessary? Another approach is say we should restrict ourselves to only the possibilities we can illuminate: we can ‘see’ whether a universe with a slightly tweaked constant is life permitting, but not wildly tweaked or alien physiced universes. So we should ignore the latter two sorts of universe and focus on the first sort – which, happily for the fine tuning argument, makes P(LPU|ASU&k’) ultra low. This is very dodgy: it amounts to an excuse to ignore your lack of epistemic access whenever it gets in the way. An analogy to make this clearer. Specks and oceans: I illuminate a one millimetre square space on an object a few trillion suns in size. The space I have illuminated is black, but with a single fleck of blue. I conclude “blue is extremely rare across the surface of this planet”, you object “this planet is vastly larger than our illuminated sample, and we have no idea of the distribution of colours – we should still say we are ignorant about how common blue is on this planet’s surface.” I reply “Not at all, the rest of this planet is outside our epistemically illuminated range – we should only consider what is within our range when making judgements.” This, I urge, is crazy.[6] Conclusion The fact life permitting universes are rare in our epistemic locality tells us nothing about how common they are in the vast space of possible universes that could have been. Therefore the fine tuning data cannot show that life permitting universes are unlikely on Atheism, and more likely on Theism. Therefore the fine tuning argument is a failure. [1] Actually, I do not think we can be that sure a perfect being wants a world of embodied moral agents. I guestimate P(LPU|T) to be ~ 0.5, with big error bars. This will come into play later. [2] I will be using this version of the argument from now on. I am confident that the objection I present refutes other variants (such as Craig 2007), with only cosmetic modification. If my opponent thinks there is a fine tuning argument that sidesteps my objection, he is welcome to offer it. [3] I grant for the sake of argument there is only one universe. [4] We need to remove from our background information a lot of stuff. This is because if we include our particular universe existing, P(LPU|this universe + anything) = 1. This will also come into play later. [5] Again, if CON thinks there is a better way of cashing out the possibility claim, he is welcome to offer it. [6] Strictly, it isn’t completely crazy. Our best estimate for the proportion of blueness on the planet is the proportion of blueness in our illuminated millimetre – this is the straight rule. However, as we get less and less confident of how representative our sample is, our confidence in the estimate should get smaller and smaller, especially so if we don’t know the probability distribution. In the case of fine tuning, where the population of possible universes is infinitely bigger than our epistemically illuminated sample, and we have no idea what the distribution of life permittingness is, our maximum likelihood estimate remains at its ultra low value, but our estimate errors are unbounded – the estimate could be any distance from this value. So our probability distribution for our estimate is an effectively uniform distribution from 0 to 1, with an infinitesimal gradient towards the ultra low value. Obviously, if so, the fine tuning argument is still screwed.