Tuesday, September 22, 2009

Demsbki's Refutation of Hume's Criticism of Paley's Design Argument: As an Argument from Analogy

David Hume argued that the teleological (design) argument for God's existence is either:

1) an argument from analogy; or
2) an inductive generalization based on a sample of size zero

These were Hume’s two main criticisms of the argument from design. The first is that the design argument is based on a weak analogy. This, says William Dembski, “is still the criticism that for many philosophers of religion remains decisive against design.” (Dembski, ID, 271) Dembski sets up the argument from analogy like this:

1. U has property Q.
2. U and V share properties A, B, C and D.
3. Therefore, V also had property Q.

Translating this into Paley’s argument we have:

1. Watches are intelligently designed.
2. Watches and organisms are similar.
3. Therefore, organisms are also intelligently designed.

The main problem with arguments from analogy is that there are also and always disanalogies. “If U and V were identical there would be no question about V having property Q if U has that property.” (Dembski, ID, 272-273) But U and V are not identical. So there are properties that U has but V does not have. And, as the argument shows, U has property Q. Does V have Q, or is this an area of disanalogy? “Without additional information the argument from analogy has no way of deciding this question.” (Ib., 273)

Dembski agrees that “if the design argument is nothing but an argument from analogy, then it is a very weak argument indeed.” (Ib.) But, say Dembski and Elliott Sober, the design argument is “much more” than an argument from analogy. Sober says it is not even an argument from analogy, but is “an inference to the best explanation.” (Ib.) Sober writes:

Hume did not think of the design argument [as an inference to the best explanation]. For him… it [was] an argument from analogy, or an inductive argument. This alternate conception of the argument makes a great deal of difference. Hume’s criticisms are quite powerful if the argument has the character he attributes to it. But if the argument is, as I maintain, an inference to the best explanation, Hume’s criticisms entirely lose their bite. (cited in Ib., 273-274)

Sober holds that Paley’s argument compares two different arguments, one argument about a watch, and a second argument about living things. The statements involved in the watch argument are:

A. The watch is intricate and well suited to the task of timekeeping.
B. The watch is the product of intelligent design. (This is one possibility)
C. The watch is the product of random physical processes. (This is a second possibility.)

Sober says that Paley is arguing that the probability of A given that B is “much bigger” than the probability of A given that C. Paley then reasons that “the same pattern of analysis applies to the following triplet of statements:” (Sober, in Ib., 274)

D. Living things are intricate and well-suited to the task of surviving and reproducing.
E. Living things are the product of intelligent design. (This is one possibility.)
F. Living things are the product of random physical processes. (This is a second possibility.)

Sober writes: “Paley argues that if you agree with him about the watch, you also should agree that” P(D/E) >> P(D/F). (Ib.) Both arguments are inferences to the best explanation. So, Sober thinks Hume’s criticism of the design argument fails.

Dembski notes that this does not lead Sober to accept the design argument, since for Sober, because of Darwin, we have a third possibility G: Living things are the product of variation and selection. Sober admits that “perhaps one day [design] will be formulated in such a way that the auxiliary assumptions it adopts are independently supported. My claim is that no [design theorist] has succeeded in doing this yet.” (Ib., 275) To which Dembski responds that the burden of his writing “has been to show that design remains a live issue and can once again be formulated as the best explanation for the origin and development of life.” (Ib.)

Yet for both Sober and Dembski Hume’s criticism fails because Paley’s design argument is not best construed as neither an argument from analogy nor an inductive argument.