Fine Tuning Argument: Why Atheists Don’t Accept It

hume
18th century Scottish philosopher David Hume, a source of the skepticism.

This one is a bit harder than my resurrection post with a similar title, for there is more than one reason. But I’d like to focus on what I think is the biggest one, one that was made clear by Richard Dawkins in The God Delusion. It’s an important topic since many think that the fine-tuning argument is the most compelling argument for God’s existence.

What is the argument? Here’s a summary from William Lane Craig taken from his debate with Lawrence Krauss:

In recent decades scientists have been stunned by the discovery that the initial conditions of our universe were fine-tuned for the existence of intelligent agents with a precision and delicacy that literally defy human comprehension. This fine-tuning is of two sorts. First, when the laws of nature are given mathematical expression, you find appearing in them certain constants, like the gravitational constant. These constants are not determined by the laws of nature. Second, in addition to these constants there are certain arbitrary quantities which are just put in as initial conditions on which the laws of nature operate, for example, the amount of entropy in the very early universe.

Now all of these constants and quantities fall into an extraordinarily narrow range of life-permitting values. Were these constants or quantities to be altered by even a hair’s breadth, the life-permitting balance would be destroyed and life would not exist. We now know that life-prohibiting universes are incomprehensibly more probable than any life-permitting universe.

Now there are three possible explanations of this extraordinary fine-tuning: physical necessity, chance, or design.

Now it can’t be due to physical necessity because, as I’ve said, the constants and quantities are independent of the laws of nature.

So maybe the fine-tuning is due to chance. After all, highly improbable events happen every day! But what serves to distinguish purely chance events from design is not simply high improbability but also the presence of an independently given pattern to which the event conforms. For example, in the movie Contact scientists are able to distinguish a signal from outer space from random noise, not simply due to its improbability but because of its conforming to the pattern of the prime numbers. The fine-tuning of the universe for intelligent agents exhibits just that combination of incomprehensible improbability and an independently given pattern that are the earmarks of design.

So, again, God’s existence is clearly more probable given the fine-tuning of the universe than it would have been without it.

What is Dawkins’s reply? He claims that chance can explain it. For he offers the tantalizing speculation popular with physicists like Lee Smolin that there are a huge (perhaps infinite) number of reproducing parallel universes, each with a different combination of initial conditions and physical constants. Those universes with black holes will reproduce more than others — these universes are also more likely to have life-permitting constants. If this is so, some universes are bound to be in the “Goldilocks range”. And Dawkins thinks that this hypothesis, though a bit extravagant and certainly speculative, is less extravagant than saying God did it, for God is an immensely complex being. And Krauss’s own response is completely analogous to the reason skeptics like Ehrman reject the resurrection of Jesus; Hume’s argument against miracles. I think that, at bottom, they are really the same response.

Let’s revisit Bayes’s Theorem:

P(G|E)/P(not-G|E) = P(G)/P(not-G) × P(E|G)/P(E|not-G)

P(G|E) is the probability of God’s existence given the evidence we are considering. P(not-G|E) is the probability of God not existing on the evidence before us. P(G) and P(not-G) is the probability of God existing or not existing just on background information; P(E|G) and P(E|not-G) is the probability of observing the evidence we do on God’s existence and God’s non-existence, that is, how much does G (or not-G) lead us to expect E, or how much does G (or not-G) explain E. What the formula says is that the ratio of the probability of God’s existence to his nonexistence is a combination of how well God leads us to expect the data as opposed to naturalism, and how probable God’s existence is just given our background information compared to naturalism.

What I think Dawkins and Krauss are saying is that even if God’s existence leads us to expect fine-tuning for life (God wants life somewhere in the universe), God’s prior probability P(G) is sooooooo low as to make God a non-starter, due to his complexity. That’s why Krauss thinks saying “God exists” is an “extraordinary claim” which requires “extraordinary evidence.” And that’s why Dawkins thinks even a wacky hypothesis like Smolin’s is better than God’s existence because, again, P(G) is soooooo low due to God’s complexity.

These are exactly the same reasons for rejecting miracles that I considered earlier, including the resurrection!! (See my post on that). So David Hume is at the bottom of all this!

Pretty much any evidence a theist might try to give for God’s existence will fall on deaf ears, for the same reasons evidence for the resurrection of Jesus will; these hypotheses have low prior probabilities.

Craig spends his time in his debates arguing for high values for P(E|G)/P(E|notG), and atheists aren’t buying because of low P(G)!

What to say about this? I think that Plantinga has given good reasons to reject Dawkins’s argument for God’s complexity implying a low P(G). Krauss doesn’t really  argue for it as much as assume it. Maybe he thinks it’s obvious. God is, after all, a rather silly being.

I have written in this post about God’s alleged low prior probability. Suffice it to say that if P(G) isn’t low, the case for God is a serious one.

Why Historians Reject the Resurrection of Jesus: It’s a Miracle

David Hume, a pillar of skepticism
David Hume, a pillar of skepticism

For a little background, check out this debate between Christian philosopher and apologist William Lane Craig and the skeptical historian Bart Ehrman. Craig argues that Jesus rose from the dead, claiming that God raising Jesus from the dead is the best explanation for these facts:

1. Jesus’ burial
2. the discovery of the empty tomb
3. his post mortem appearances (at least in the minds of the disciples)
4. the origin of the disciples’ belief in his resurrection

What is interesting is that in the debates against Craig, the core of the response of Craig’s opponents isn’t about disputing these facts. Their main argument is that God raising Jesus from the dead (call this the Resurrection Hypothesis, or RH) is not historical because it is a miracle claim.

One might think that this is just anti-religious prejudice. But they do offer a philosophical argument for the prejudice. It’s the 18th century philosopher David Hume’s argument against belief in miracles (Ehrman in the above debate denies this, but his argument is pretty much a simplified version of Hume’s argument).

What is Hume’s argument? Here’s a quote:

When anyone tells me, that he saw a dead man restored to life, I immediately consider with myself, whether it be more probable, that this person should either deceive or be deceived, or that the fact, which he relates, should really have happened. I weigh the one miracle against the other; and according to the superiority, which I discover, I pronounce my decision, and always reject the greater miracle. If the falsehood of his testimony would be more miraculous, than the event which he relates; then, and not till then, can he pretend to command my belief or opinion. (Hume 1748/2000: 87–88)

There is much dispute between Hume scholars about what this argument amounts to (see this article in the Stanford Encyclopedia of Philosophy). But let’s consider this question using probability theory.

I have two versions of what follows, hard, and easy. Here’s hard (skip if you don’t want to go through the math):

Consider one formulation of Bayes’ Theorem:

P(RH|E) = P(RH) × P(E|RH)/P(E)

I’ll describe what this means. RH = God raised Jesus from the dead. E is the evidence now under consideration (background information understood to be always there and is not included in the formula). P(RH) is the probability of RH just in itself, without considering the evidence at hand (This is called the “prior probability”). P(RH|E) is the probability of RH given E (the probability of RH given the evidence). P(E|RH) is the probability of the evidence occurring if RH is true. This term is about the explanatory power of RH — RH accounts for E if RH gives one reason to expect E. That is, if RH gives us reason to expect E, then E’s occurring is evidence for RH. Finally, P(E) is the probability of E just given the background information. It is to normalize the equation. There is also the intuition that P(E|RH), even if high, wouldn’t mean much if we would expect E to happen anyway. Thus we divide P(E|RH) by P(E).

My own view is that Hume’s argument amounts to this: P(RH) is extremely low. That is, the probability of a miracle occurring, given our background information (including all of science), is low, for miracles are, by definition, a violation of the regularities of experience. Thus all of experience stands against them. If that’s true, then P(E|RH)/P(E) would have to be extraordinarily high to compensate if the Resurrection is to have any real probability of happening. In the real world no one could supply such evidence.

Here’s easy:

Two main things go into how probable some statement is given the evidence. The first is how inherently likely the statement is, without considering evidence. Let’s call this the prior probability. The second is how much does the evidence support the statement. With miracles, skeptics, like Hume, argue that their prior probability is sooooo low that no amount of evidence can make them reasonable to accept. The Resurrection of Jesus is no exception. We could grant that the evidence does give some support for the claim, but still reject the claim because it’s so inherently unlikely. It’s like trying to prove that someone saw an alien. The evidence that would be enough for an ordinary event wouldn’t be enough for something extraordinary like the appearance of an alien. As atheists and skeptics often say, “Extraordinary claims demand extraordinary evidence.”

Back to the main topic:

Though skeptics might admit that natural alternative explanations of the data surrounding Jesus’ resurrection have so far been disappointing, they would insist that even the worst of these is better than the Resurrection (Ehrman was explicit about this), presumably because of the Resurrection’s low prior probability.

Craig admits that, just by itself, the Resurrection is very improbable. Craig asserts, however, that he isn’t arguing merely that Jesus rose from the dead, but that God raised Jesus from the dead.1 This latter statement, at first, seems to have a higher prior probability: God would have the power to do something that has no precedent in experience. A skeptic, however, could reply that adding God into the hypothesis makes it more complex, lowering the prior probability. The more ad hoc additions we make to a theory, the worse it is in terms of prior probability.

Notwithstanding, Craig spends most of his time arguing for a high value for P(E|RH)/P(E) (arguing that the evidence is well explained by the hypothesis) — he argues that the evidence given above is far more probable on the Resurrection than on any natural hypothesis. But all this falls on deaf ears because of the low value of P(RH) (low prior probability).

What can be said? I think that P(RH) (the Resurrection’s prior probability) is low given naturalism. Adding God to the hypothesis seems ad hoc. But what if we had independent evidence for God’s existence? If God exists, then, given His goodness and the evil in the world, we might expect some sort of action on his part to address this evil. In particular, we could expect some sort of revelation. And for us to know the revelation was from God, we might expect some sort of miracle to validate the revelation. So we would be expecting something like RH (the Resurrection Hypotheis).2 This wouldn’t show that Jesus rose from the dead, but it would mitigate the low prior probability for RH: God wouldn’t just be some add on, but something independently supported. Then evidence for the Resurrection could be taken more seriously.

Thus I think that the case for Jesus’ resurrection by God needs to be made as part of a comprehensive case for Christianity. This would include a case for God’s existence as the best way to account for all the data of our experience (including our apprehension of a realm of value, our experience of ourselves as immaterial beings, the existence and fine-tuning of the universe, etc). This is, of course, what Craig does in God debates. However, I don’t think it appropriate to use Jesus’ resurrection as evidence for God (as Craig does) simply because Jesus’ resurrection would only be the best explanation for the facts he presents as evidence if we already knew that God exits. It would be a circular (or pretty close to circular) argument. I would instead try to argue for God’s existence, then, if successful, use evidence for the Resurrection to support the truth of Christianity.

  1. Craig also denies that Bayes’ theorem is applicable to historical analysis, as these probabilities cannot be determined. See his debate with Greg Cavin here: https://www.youtube.com/watch?v=Rmxi9o_xqkc.
  2. Similar ideas are worked out in Richard Swinburne’s Revelation.