In the words of cosmologists Hawley and Holcomb, “if the intent of the universe is to create life, then it has done so in a very inefficient manner,” unlike the cosmos Aristotle once honestly thought there was, which had “a much greater amount of life per cubic centimeter” (and that's an understatement: its “life per cubic centimeter” would be on the order of 10
30
times greater than ours).
25
In Aristotle's world, the atmosphere of the earth extended to the moon, and even beyond that the whole universe was filled with a special breathable medium that was fully inhabited by animals suited thereto. We can as easily imagine a universe of any size in which the whole of it has breathable air and places to fly and rest and eat and drink, or in which the whole of it was filled with water (after all, let's not bias the options in favor of us newbie air-breathers) or a vacuum that wasn't lethal (if life didn't need to breathe but took all its sustenance directly from the rays of the sun)—or anything else or in between.
26
One way or another, a universe perfectly designed for life would easily, readily, and abundantly produce and sustain life. Most of the contents of that universe would be conducive to life or benefit life. Yet that's not what we see. Instead, almost the entire universe is lethal to life—in fact, if we put all the lethal vacuum of outer space swamped with deadly radiation into an area the size of a house, you would never find the comparably microscopic speck of area that sustains life (it would literally be smaller than a single proton). It's exceedingly difficult to imagine a universe
less
conducive to life than that—indeed, that's about as close to being completely incapable of producing life as any random universe can be expected to be, other than of course being completely incapable of producing life. But, as already explained, we already know we're not in one of
those
universes, so we can rule them out, just as a lottery winner can rule out the possibility of his losing the lottery and then only compare wins that resulted from chance with wins that resulted from cheating—since it is only that ratio that determines the probability that his win was by design and not by chance.
For example, if 1 in 100 lottery wins are by design, and the remainder by chance, then the probability that an observed win is by design is simply 1 in 100, no matter
how improbable that win is.
Even if the odds of winning were 1 in 10
1
'
000
'
000
. For even then, if it's still the case that 99 in 100 wins are the product of chance, then the odds that
this
win is the result of chance are not 1 in 10
1
'
000
'
000
but 99 percent. That's why we never assume anything is fishy when we draw an amazing hand at a family game of poker. The probability of doing so may be 1 in 100,000, but it doesn't follow that the odds of it being by design are then the converse of that (a 99.999 percent chance the hand is rigged), because we already know most amazing hands are fair. Thus if we know less than 1 in 1,000 amazing hands are rigged, and then draw an amazing hand that is 100,000 to 1 against, the probability of that hand being rigged is still only 0.1 percent (1 in 1,000), not 99.999 percent. To carry the analogy over, how many actual life-bearing universes are the product of chance? If there is no God, then 100 percent of them will be. Thus, where L = “a kind of life-bearing universe exists whose odds of existing without a god are 1 in 10
1
'
000,000
,” it is
necessarily the case
that the probability that we would observe L if there is no God is fully 100 percent, not 1 in 10
1
'
000
'
000
.
27
Yet the most we can ever get for the God hypothesis is still only the same 100 percent probability that L would be true.
28
And if that's the case, then Bayes’ theorem gives us a probability that NID caused the universe of only 25 percent.
29
There is then only a 25 percent chance
at best
that the cosmos was finely tuned by design. This means it probably wasn't. More likely, it was finely tuned by chance (more than 75 percent likely, in fact).
This conclusion cannot rationally be denied. Nevertheless, attempts to deny it have been made, occasionally using a firing squad analogy (discussed by both Sober and Collins).
30
But that analogy is inapplicable because it assumes the existence of an intentional agent (the firing squad) and thus is merely an exercise in deducing that agent's intent (whether that squad “chose” to miss you). We are not in that situation but in that of trying to deduce whether a firing squad even exists in the first place. So we cannot presume there is one. There are other differences that render that analogy inapt, but this is the most pertinent. A more apt analogy would be: you are placed in front of a strange machine that shoots thousands of bullets around the room at random. Was it designed to miss you? Here answering that question must rely on your background knowledge about strange complex events: are they usually freak accidents or products of intelligent design? Once we rule out terrestrial design (as we must in the universe example) and alien design (as we have stipulated), we are left with no established instances of intelligent design even for complex events, thus our prior probability must reflect that such instances are exceedingly rare (like instances of rigging amazing poker hands in a family game).
31
If they ever even happen at all.
For example, suppose we knew in advance that 1 in 4 such machines was rigged to miss, and that the chance of their missing by accident was 1 in 100. Then we would infer design, because in any cohort of 1,000 victims, on average 250 will survive by design and only 10 will survive by chance, so if you are a survivor your prior odds of having survived by chance are 10 in 260, or barely 4 percent. From that prior probability you should conclude design, even when the evidence (your not getting hit) is the same either way.
32
But suppose you knew in advance that only one in four
results
was a product of design, and the others were of chance. Then in any cohort of a thousand victims you will still know there are on average ten survivors by chance, but you will also know that for every survivor there is who survived by design, three
more
will have survived by chance, so you will know there can be, on average, only three who survived by design—so if you are a survivor, your odds of having survived by chance are still three in four or 75 percent. In this case, you
shouldn't
conclude design—and that's even knowing the odds of having survived by chance are 1 in 100. So in that case, as in the scenario just analyzed for our universe, the probability that the machine was designed to miss you is still 25 percent no matter how unlikely its missing you was. Thus also for our universe: in our background knowledge we have no evidence that the frequency of very improbable events (not already caused by known life) being products of NID is anything higher than 25 percent. It doesn't matter how improbable any of those events are (like the odds of our solar system being arranged in just the way it is: far lower than 25 percent, yet still not a product of NID). Thus we cannot conclude the probability that the universe is a product of NID is anything higher than its prior probability of 25 percent. This remains a fact no matter how improbable the universe is.
33
And yet even that 25 percent is much too high. Our universe looks exactly like what random chance would produce, but not exactly like what intelligent design would produce. Given all the actual observed properties of the universe (its vast age, size, scale of lethality, and inefficiency at producing life), which are exactly what we expect if no god designed it but not exactly what we'd expect if a god did (since there is no way you can deduce from “a very powerful self-existent being created the universe by design” that the only way he would ever do it is with such vast age, size, lethality, and inefficiency at producing life), the probability that the universe would then be as we observe it
must
be less than 100 percent. Given that there are so many more obvious ways a god could make a life-bearing universe (as sampled earlier), which would be vastly more life-friendly and life-appropriate, and which would not look suspiciously exactly the same as a universe must look if there was no god at all, that probability must be
substantially
less than 100 percent. No rational person can honestly believe it's any greater than 50 percent (because there's no way that outcome is even “50-50” on that hypothesis).
This entails the Bayesian conclusion that the probability that God intelligently designed the universe cannot be any higher than 15 percent (and is almost certainly a great deal less than that).
34
That means no rational person can believe the probability that God intelligently designed the universe is any better than 1 in 6. This means every rational person must conclude God probably didn't do that. The universe thus does not appear to be intelligently designed. Quite to the contrary, it looks exactly like a chance accident.
OTHER KINDS OF APPARENT DESIGN
So the universe probably wasn't designed by god, either. What about other things? Aren't there other things that exhibit divine design, things other than life or the universe per se?
What about the human mind? That already has a better explanation in natural causes, being a product of neurophysics and evolution. The scientific knowledge confirming this has vastly increased in just the last fifteen years, so it can't reasonably be denied anymore.
35
The dependence of the mind on a working brain is now an established fact in our background knowledge. We have identified where in our brain different kinds of memories are stored, where emotions and reason operate, where each kind of sensory experience is processed, and so on. We have observed that if we physically remove or deactivate any one of these parts, the memories or abilities it contains then cease. It follows that if we take away all the parts, everything that we are will cease. Comparative anatomy with animals verifies every point.
36
If the brain is not a product of NID then all of this
must
be the case, since on the absence of NID there is no other way to have consciousness except as the product of a large, delicate, and complex physical system like our brain, a system that appears only at the end of an extremely long process of trial and error as brains increased in size, complexity, and capability over the course of half a billion years.
Such evidence of our brain-produced and brain-dependent mind is thus 100 percent expected on the absence of NID. But it's not 100 percent what we'd expect on NID. If God doesn't need a brain, neither should we. We would more likely be made “in god's image,” but that's not what we observe. God could have provided every human being with a brainless mind that doesn't need food or oxygen, that is incapable of being damaged by any wounds or disease, that always perceives and reasons and remembers correctly, that doesn't pose a physical threat to a mother's life or health during delivery (as human brains do, being so relatively large, as human brains need to be to do all the complex things the human mind does but that other animals don't),
and
that is otherwise in every respect the same as our current mind. Or he could have made any other mind to any degree in between that one and the one we have. Whereas on the absence of NID we could
only
have the kind of mind-brain system we do, on NID we could have had many other kinds of minds, and some of them are even more likely on NID. So the probability we'd observe the kind of brain-dependent mind we do if it was a product of NID must be less than 100 percent, in fact certainly not greater than 50 percent (since we can't predict from “god did it” even a 50-50 chance that this is what he'd do, as opposed to all the other options available to him).
37
Thus we get the same result here we've always gotten: there cannot possibly be more than a 15 percent chance that our mind was designed by God.
38
It might be objected that there is one aspect of mind that can't yet be predicted by known science: qualia (the immanent qualities of conscious experience). But it does not follow that qualia are improbable on NID.
39
This is because their proximate causes have not been verified and thus we do not know what the probability of qualia actually is in the absence of NID, much less that it's less than 100 percent. Just as with fine-tuning, if every comparable brain produces qualia (just as every finely tuned universe produces life), then the probability of our observing qualia in the absence of NID is fully 100 percent.
40
And, for all we know, that could well be the case.
41
And whether it's 100 percent even on NID is not logically assured. If people can be philosophical zombies (minds without qualia), so can God; and so can God make philosophical zombies of us.
Scientifically speaking, the God hypothesis is not likely to fare well in the future; after all, we can already deduce from known scientific facts and the presumed absence of NID many features of qualitative experience (such as why we don't normally smell in color or why we see the specific colors we do and not others—including colors we “see” but that don't really exist as specific frequencies of light, like magenta), whereas we could never have predicted those things from NID and still cannot.
42
So far, every cause of mental phenomena discovered has not been NID, so the prior probability that any remaining phenomena will be explained by NID is continually shrinking. But even setting that aside, we have no knowledge in
b
that renders qualia any more likely on NID than on its absence, so qualia make no difference to the above calculation. There is no more evidence to show that qualia are impossible on the absence of NID than that qualia are inevitable on the absence of NID. We can at best split the difference and say it's 50 percent.
43
But we must say the same for NID, because we can only get, for example, “god experiences qualia, too” or “god wants us to experience qualia,” by assuming that's the case ad hoc (since we don't actually have any evidence of the fact), which halves the prior probability (since so far as we honestly know, there is at best a 50-50 chance that “a very powerful self-existent being who creates things by design” does either, much less both), and if we
don't
assume either theoretical element ad hoc, then the probability of qualia on NID is still only 50 percent.
44
Either way, the math comes out the same.
45
Qualia simply do not argue for or against NID.