Understanding the finetuning

Our next question is this: Does the multiverse hypothesis undercut the case for some sort of design from fine-tuning, as advocated by various thinkers [9]? I will argue that, at most, it mitigates the case by rendering it less quantitative. First, however, we will need to sketch the fine-tuning argument itself.

Fine-tuning has been widely claimed to provide evidence of, or at least suggest, some sort of divine design of the Universe. Elsewhere, I have attempted to develop this argument in a more principled way [10]. As I develop it, the 'core version' of the argument essentially involves claiming that the existence of intelligent-life-permitting values for the constants of physics is not surprising under theism, but highly surprising under the non-design, non-multiverse hypothesis - that is, the hypothesis that there is only a single universe and that it exists as a brute fact without any further explanation. Further, the reason it seems highly surprising under the non-design, non-multiverse hypothesis is that, for certain constants of physics, the range of intelligent life-permitting values is purportedly small compared with some non-arbitrarily defined comparison range - such as the range of force strengths in nature when discussing the fine-tuning of gravity and other forces.

Using what could be called the 'surprise principle', it follows that the existence of intelligent-life-permitting values for the constants provides evidence in favour of theism over the non-design, non-multiverse hypothesis.3 Note that no claim is being made here that theism is the best explanation of the constants being intelligent-life-permitting. To judge that a hypothesis is the best explanation of a body of data involves an overall assessment of the hypothesis, not simply how well it explains the particular data in

3 The surprise principle can be stated as follows. Let H1 and H2 be two competing non-ad-hoc hypotheses; that is, hypotheses that were not constructed merely to account for the data E in question. According to the surprise principle, if a body of data E is less surprising under hypotheses H1 than H2, then the data E provides evidence in favour of H1 over H2. The best way, I believe, of explicating what the notion of surprise is here is in terms of what philosophers call conditional epistemic probability, in which case the above principle becomes a version of the likelihood principle or the principle of relevance, which is a standard principle of probabilistic confirmation theory (see, e.g., ref. [11]). Unlike what D. H. Mellor [12] assumes in his objection to Martin Rees's claim that cosmic fine-tuning supports the multiverse hypothesis, conditional epistemic probability is not a measure of ignorance. Rather, it has to do with relations of support or justification between propositions. As John Maynard Keynes stated in his treatise on probability [13], 'if a knowledge of h justifies a rational belief in a of degree a, we say that there is a 'probability-relation' of degree a between a and h'. Although I think Keynes's account needs further work, I believe it is on the right track. For a recent development of this notion of conditional epistemic probability, see ref. [14].

question. The fact that Johnny's fingerprints are on the murder weapon might significantly support the claim that Johnny committed the murder. Nonetheless, Johnny's committing the murder might not be the best explanation of the fingerprints, since we might have strong, countervailing evidence that he did not commit the murder. Perhaps, for instance, five reliable witnesses saw Johnny at a party at the time of the murder. Similarly, all I claim is that the evidence of fine-tuning supports theism over the non-design, non-multiverse hypothesis. However, to judge whether we should infer that theism is the best explanation of the structure of the Universe - versus simply accepting the Universe as a brute given - involves many factors beyond the evidence of fine-tuning.

One of the key claims in the above argument is that the existence of a universe with intelligent-life-permitting cosmic conditions is not surprising under theism. This claim needs support instead of merely being assumed in an ad hoc way. Essentially, the argument is that if God is good - an assumption that is part of classical theism - then it is not surprising that God would create a world with intelligent beings, because the existence of such beings has positive value, at least under the theistic hypothesis.

Philosophers of religion offer a variety of justifications for the claim that God is perfectly good, or at least why ascribing goodness to God is not arbitrary. Here I will simply present two. First, some philosophers appeal to the Anselmian conception of God mentioned above, arguing that a being that is perfectly good is greater than one that is not perfectly good, and hence the characteristic of perfect goodness should be ascribed to God. Second, other philosophers - such as Richard Swinburne [15] - argue that, once grasped, the goodness or beauty of a state of affairs gives any conscious agent a reason to prefer that state of affairs. The idea is that part of grasping that a state of affairs has value - whether moral or aesthetic - is to 'feel' the desirability of the state, and hence have some motivation to bring it about. Under this view, for instance, people only do evil either because they do not grasp the disvalue of doing evil, or because some other influence tempts them to do what they recognize as having ethical disvalue. Since God is perfectly free -that is, God is not subject to countervailing desires in the way we are - God would have no motive to act against the good or beautiful. So, we would naturally expect God to act to bring about states of beauty and goodness. Whether one buys this sort of argument or not, I think that at minimum one has to admit that it is in no way arbitrary or ad hoc to hold that God has the desire to bring about states of goodness and beauty.

If this is right, then theism provides a natural connection between the moral and aesthetic realms of value and any such value we might have reason to believe that the Universe is structured to realize. One need not necessarily invoke a personal God to provide this connection, however. John Leslie [16], for instance, proposes what he calls a 'neo-Platonic principle of ethical requiredness', as suggested by Book VI of Plato's Republic, which could be thought of as a 'God substitute'. According to this principle, what ought to exist does exist. Further, Leslie claims, this principle exists as a matter of metaphysical necessity, much as many philosophers view the truths of mathematics, such as 2 + 2 = 4. Thus its existence is self-explanatory. Leslie points out, however, that his neo-Platonic principle is compatible with theism, and might even entail theism: since God is a being of supreme value, one could argue that the principle entails that God would exist. Thus, even if we adopt Leslie's hypothesis, this would not necessarily provide an alternative to the theistic explanation of the fine-tuning of the Universe.4

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