Premise 1. The existence of the fine-tuning is not improbable under theism.
Premise 2. The existence of the fine-tuning is very improbable under the atheistic single universe hypothesis.
Conclusion: From premises (1) and (2) and the prime principle of confirmation, it follows that the fine tuning argument provides strong evidence to favor the design hypothesis over the atheistic single universe hypothesis (Collins, 2003: 125).
The “prime principle of confirmation (PPC)” is defined by Collins:
Simply put, the principle says that whenever we are considering two competing hypotheses, an observation counts as evidence in favor of the hypothesis under which the observation has the highest probability (or is the least improbable). (Or, put slightly differently, the principle says that whenever we are considering two competing hypotheses, H1 and H2, an observation, O, counts as evidence in favor of H1 over H2 if O is more probable under H1 than it is under H2.) Moreover, the degree to which the evidence counts in favor of one hypothesis over another is proportional to the degree to which the observation is more probably under the one hypothesis than the other (Collins, 2003: 123-4; emphasis in original).
Collins regards his first premise as relatively uncontroversial. Surely, it seems, a perfectly good God would want intelligent, conscious beings to exist, and so would create a world friendly to the development of such life. Collins thinks that most criticisms will be directed at the second premise. For instance, atheists could argue that since there is only one universe, the idea that the fundamental constants of nature are improbable is meaningless. In this case the PPC could not be applied to favor theism over the ASUH, since, on this latter hypothesis, there is no probability, high or low, that the universe is fine tuned, and so the fact of fine tuning cannot be more probable given theism than given the ASUH.
I have argued in favor of the ASUH:
The assignment of meaningful probabilities upon the hypothesis of atheism is…difficult. If atheism is correct, if the universe and its laws are all that is or ever has been, how can it be said that the universe, with all of its “finely tuned” features, is in any relevant sense probable or improbable? Ex hypothesi there are no antecedent conditions that could determine such a probability. Hence, if the universe is the ultimate brute fact, it is neither likely nor unlikely, probable or improbable; it simply is…If we were in a position to witness the birth of many worlds—some designed, some undesigned—then we might be in a position to say of any particular world that it had such-and-such a probability of existing undesigned. But we simply are not in such a position. We have absolutely no empirical basis for assigning probabilities to ultimate facts (Parsons, 1990: 182).
So, if there is no meaningful sense in which the “finely tuned” features of the universe are either probable or improbable given the ASUH, then those features cannot confirm theism over atheism.
Collins replies that the sense of probability relevant to the FTA is epistemic probability, which he characterizes as follows:
Roughly, the epistemic probability of a proposition can be thought of as the degree of confidence or belief we rationally should have in the proposition. Further, the conditional epistemic probability of a proposition R on another proposition S—written as P(R/S)—can be defined as the degree to which the proposition S of itself should rationally lead us to expect that R is true. Under the epistemic conception of probability, therefore, the statement that the fine tuning of the cosmos is very improbable under the [ASUH] is to be understood as making a statement about the degree to which the [ASUH] would or should, of itself, lead us to expect cosmic fine-tuning (Collins, 2007:355; emphasis in original).
In other words, the relevant question is this: Given only the information contained within the ASUH—that only one universe exists as an ultimate brute fact—and no other information at all (such as the fact that we are alive, and so the universe must be life-friendly), to what degree should we rationally expect the basic constants of the universe to be finely tuned?
Collins answers that the rational expectation of fine-tuning given only the ASUH is much lower than it would be given theism. He imagines a disembodied being who is highly intelligent and thoroughly familiar with the laws of physics as known today, but who does not know whether the actual values of the physical constants are such as to allow complex embodied life (CEL). Collins says that such a being would have a much greater rational expectation that those constants would fall within the range permitting CEL given theism than given the ASUH:
…it is not difficult to see that the conditional epistemic probability of a constant of physics having a CEL-permitting value under the [ASUH] will be much smaller than under theism. The reason is simple when we think about our imaginary disembodied being. If such a being were a theist, it would have
some reason to believe that the values of constants would fall into the CEL-permitting region…On the other hand, if the being were a subscriber to the [ASUH], it would have no reason to think the value would be in the CEL-permitting region instead of any other part of the “theoretically possible” region R. Thus, the being has more reason to believe the constants would fall into the CEL-permitting region under theism than the [ASUH], or put differently, the existence of a CEL-permitting universe is more surprising under the [ASUH] than theism (Collins, 2007: 356).
In short, the finely-tuned features of the universe are more probable (rationally expected) given theism than given the ASUH, so, the PPC tells us that the existence of those features counts much more strongly in favor of the hypothesis of theism than the ASUH.
Collins’ chief disagreement with the proponents of the ASUH will be over whether we can have rational expectations about ultimate metaphysical posits. The ASUH posits the primordial condition of the universe, encompassing the universe’s initial state and its physical laws, as ultimate brute facts. To posit something as an ultimate brute fact is to say, inter alia, that it is not caused by, derived from, reducible to, composed of, conditioned by, an epiphenomenon of, or supervenient upon anything else. In other words, an ultimate brute fact is a sheer given: A basic or primordial reality that is not in any sense dependent upon or explicable in terms of any antecedent or more fundamental reality. This means that proponents of the ASUH regard the values of the constants as ultimate brute facts or hold that those values are determined by deeper laws (perhaps to be described by the vaunted “Theory of Everything”) which themselves are posited as ultimate brute facts. If the finely-tuned nature of the universe is thus an ultimate brute fact, then there can be no objective basis for regarding any value of those constants, or any range of those values, as having any probability at all. As defenders of the ASUH see it, rational expectations must have a rational basis, that is, some information of a theoretical or empirical nature to provide grounds for the expectation. Yet, when we are talking about ultimate posits, then, ex hypothesi, all such information has been withheld. Therefore, it seems that we must say that the values of the constants are neither probable nor improbable; they just are. In that case, as the proponent of the ASUH sees it, the only rational expectation of the values of the constants is that they will be whatever we find them to be.
Collins, however, does think that there can be a rational basis for an expectation of the values of the constants given ASUH. He appeals to the principle of indifference, which he characterizes as follows:
Applied to the case at hand, the principle of indifference could be roughly stated as follows: when we have no reason to prefer any one value of a parameter over other, [sic] we should assign equal probabilities to equal ranges of the parameter given that the parameter in question directly corresponds to some physical magnitude (Collins, 2003: 129; emphasis in original).
He next shows how this principle would apply in forming our rational expectation about the value of the gravitational constant:
Specifically, if the “theoretically possible” range (that is, the range allowed by the relevant background theories) of such a parameter is R and the life-permitting range is r, then the probability is r/R Suppose, for instance, that the “theoretically possible range, R, of values for the strength of gravity is zero to the strength of the strong nuclear force between those protons—that is, 0 to 1040G0, where G0 represents the current value for the strength of gravity. As we saw above, the life-permitting range for the strength of gravity is at most to 109G0…Thus, assuming the strength of the forces constitute a real physical magnitude, the principle of indifference would state that the equal ranges of this force should be given equal probabilities, and hence the probability of it the [sic] strength of gravity falling into the life-permitting region would be at most r/R = 109/1040 = 1/1031 (Collins, 2003: 129).
It appears, then, that if we accept the principle of indifference, and given only the ASUH, our rational expectation that the values of the gravitational constant would fall within the CEL-permitting region would be only about one in 1031, a very small expectation indeed.
Many objections have been raised against the principle of indifference. Some of them are rather technical, and an examination of these and Collins’ responses is beyond our scope here (see Collins, 2003). Unquestionably, there are contexts where, when properly restricted, the principle of indifference is useful in solving certain problems and performing certain calculations of probability (see, e.g., Applebaum, 1996: 52-3). The crucial question is not whether that principle is ever useful, but whether it can do the metaphysical heavy lifting that Collins wants it to do. Clearly, it is quite a leap to think that a principle useful in certain rather modest and restricted contexts can provide information in such an outré context as providing rational expectations about what we would otherwise deem metaphysical imponderables.
Can we have rational expectations about ultimate metaphysical posits? It may help to note that the defenders of the ASUH have one thing in common with theists—each group posits something as a brute, inexplicable, metaphysical ultimate. For ASUH supporters, it is the primordial state and laws of the universe; for theists it is God. John Hick states this point clearly:
It is true that no naturalistic theory can account for the existence of the universe, or for its having the basic character that it has; this simply has to be accepted as the ultimate inexplicable fact. But religion also has its ultimate inexplicable fact in the form of God or a non-personal Absolute. And the skeptical mind prefers to rest in the mystery of the visible world without going beyond it to a further invisible mystery (Hick, 2004: 111).
Further, it seems that in either the naturalistic or the theistic case we can imagine possible worlds in which things are different. We can imagine possible worlds in
which the values of the fundamental physical constants are other than they are in the actual world. Likewise, we seem to be able to imagine possible worlds in which something other than the theistic God would be the ultimate, uncaused, brute supernatural reality. Indeed, it seems that there could have been (i.e., there seem to be possible worlds in which) one or more of an indefinitely numerous set of supernatural entities could be the ultimate existent(s) instead of the theistic God. Maybe, for instance, there could have been Platonic ideas, or a neo-Platonic One, or a being totally indifferent to created beings, or, tragically, a lonely god who yearns for companionship, but does not have the power to create.
The upshot is that if it is possible to have rational expectations about which of a range of possible worlds is likely to be actualized, where do we stop? If someone insists that we are very, very lucky—impossibly lucky—to have a universe as “life friendly” as the one we inhabit, and therefore there must have been a supernatural fine-tuner to set things up, don’t we have to ask why that same reasoning should not apply to putative supernatural beings? Why is it, that of all the ultimate, uncaused supernatural beings that might have existed, we were so impossibly lucky as to get one that was a personal being who, amazingly, just happened to want creatures like us and also had the power to do the fine tuning? Instead of solving the fine-tuning problem, doesn’t the hypothesis of theism merely set it back a step? Instead of a finely-tuned universe we seem to need a finely-tuned God. If the former is wildly unlikely, then why not the latter? If the universe is rationally unexpected, then why not God?
Theistic philosophers have historically recognized the force of such queries and have attempted to obviate them by countering that the theistic God is in some sense uniquely ultimate so that his existence is not a metaphysical mystery in the sense that any other postulated ultimate would be. Some have postulated that God is logically necessary or is the only being that is its own sufficient reason. Some, like Richard Swinburne (1979) argue that the hypothesis that posits God as the ultimate inexplicable existent is a simpler hypothesis than any other, and therefore more a priori likely. Each such suggestion has very serious problems that we do not have space to pursue here (but see Mackie, 1982, Parsons, 1989, and Oppy, 2006).