Likelihood of Design

At first blush, the likelihood approach favors intelligent design over evolution. Surely the observation of complex adaptations like eyes is far more probable given the existence of an intelligent design or a creator god than it would be given natural processes such as chance mutation and natural selection. On the other hand, a closer look at the assumptions involved in this argument will reveal that it is circular.

Sober (2002a, 306-309) presents the following objection (citing Keynes (1921) and Venn (1866) as having presented the objection before, and Hume for the basic formulation of the idea). How probable is it that the human eye, for example, would have the features it has, given that it was intelligently designed, versus given that it is the result of evolution? Asking about the probability that the human eye has the features it has, given that it was intelligently designed really calls into question the intentions of the designer.

Consider Paley's watch, again. How one answers 'What are the chances that the watch I have just found in this field would have the features it does, given that it was intelligently designed?' changes depending on what one thinks the designer intended, not to mention what one thinks of the designer's abilities. If one thinks that the designer intended to make a device which would tell time, and was able to construct such a device, then the chances are quite good; however, if one thinks that the designer intended to make a device which would cook a roast, and was able to do so, then the chances are quite poor.

The trouble is, really, that one is invoking intelligence and ability in designing a specific thing for a specific purpose. But there are any number of purposes in designing things, not to mention a wide range of abilities to consider, in this case from natural to supernatural abilities. If the intelligent designer wished to design the eye to do what it does, and was able, then the probability of observing a well-adapted eye, given an intelligent designer is 100%. However, if the design goals differ, or if the ability level differs, the probability may drop. As Sober (2002a, 306) points out:

There are as many likelihoods as there are suppositions concerning the goals and abilities of the putative designer. Which of these, or which class of these, should we take seriously?

To assume in one's argument for Intelligent Design that the intelligent designer's purpose was to make the eye to do exactly what it does begs the question. It is no good to attempt to prove that there was a designer who intended to and was able to create the eye by assuming that there was a designer who intended to and was able to create the eye. One requires independent evidence that the designer intended to and was able to create the eye, because the existence of the eye is precisely what one is trying to explain; one cannot merely assume it has been so created, because that assumes what one is trying to prove. This would be like trying to prove in a court of law that Jones intended to and was able to murder Smith, merely by saying that Jones was able to and intended to murder Smith --- without providing any corroborating evidence.

We cannot turn to scripture or revelation for such evidence, because granting the credibility of that kind of evidence already grants the existence of what one is trying to prove.

It may be objected that we do make certain assumptions about the putative abilities and goals of other beings in the search for extra-terrestrial intelligence (SETI). Doesn't SETI research assume that we could impress upon other beings that the signals we are sending out are intelligently designed, and that signals we receive could be analyzed to find out whether they were intelligently designed?

Sober (2002a, 306-307) handles this objection thus: in the SETI case, we assume that alien minds will work like our own --- what else can we do? Even then, there is no guarantee that this assumption will hold true, and thus the possibility that signals we send and possibly could be receiving now will be not be interpreted as the product of design, is a very real possibility. And if failure to anticipate the abilities and intentions of aliens (presumably natural beings) is a real possibility, how much more difficult would it be to anticipate the abilities and intentions of a possibly supernatural being?

All this is not to say that belief in God or an intelligent designer is not acceptable or even rational. All we have here concluded is that one cannot prove empirically by intelligent design arguments that God or an intelligent designer exists, nor can one even show empirically that the existence of God or an intelligent designer is a more likely hypothesis than mere natural processes like evolution, given what we see in the world around us. Thus it is wrongheaded to adopt textbooks in the public schools which argue that this is the case.

It should be apparent by now that the Intelligent Design argument fails, and that the attacks on Evolution Theory are not strong enough to call it into question. I hope by this time you would at least consider that God or an intelligent designer could operate through evolutionary processes. On that hope, I ask you to proceed to Why Not Through Evolution Or Chance?.