>In fact, it's Dembski, Behe or other ID people who should answer this. I just answered you because I got the impression that you misrepresented their position. I still think a viable partial system would necessarily indicate that the whole system (of which it is a part) cannot be irreducibly complex - by Behe's definition. Dembski's explanatory filter involves 3 tests (W.A. Dembski, in: "Mere Creation" (InterVarsity Press, 1998), pp. 93 ff): (1) is the system highly probable (explanation: law)? If not, (2) is it of intermediate probability (explanation: chance)? If not, (3) is it specified in advance (explanation: design)? If not, it happened by chance. If yes, it has specified complexity (according to Dembski), or is irreducibly complex (according to Behe). If there is a viable evolutionary precursor, the system doesn't pass test 2 of the Dembski filter (but this precursor, in turn, may then have to be tested for irreducible complexity).
>You are right in doubting that irreducibility can be proven. You can hardly ever prove that there cannot be any viable evolutionary precursor - you just might find one some day. Negatives in this sense usually cannot be proven. But all Dembski claims is inference to the most probable cause.
>Peter Ruest <email@example.com>
I think we are basically agreeing that absolute lack of viable intermediates would be a good criterion for irreducible complexity. My point is that the criteria actually used to purportedly recognize intelligent design do not come close to eliminating the possibility of viable intermediates.
We cannot specify the complexity of an existing biological system ahead of time, because they already exist. (Some time ago, Dembski put in an appearance on this list. I raised this question and he replied that his next book would answer it. I have not tried to watch everything he published since, but cannot think on my own of a way to specify in advance something that already exists.) A valid argument for specified complexity also requires a priori statistical planning. You cannot just keep looking for something that matches your specifications until you find it and then consider that significant. For example, suppose I am trying to build a stone wall without mortar. As I come close to finishing it, I will need rocks of particular sizes and shapes to fill in gaps. Assuming that I had enough sense to build my wall somewhere where rocks are abundant, I can hunt around and find rocks that meet my established specifications. I may look at hundreds of rocks before findi!
ng the right one, and thus I have no reason to consider the rock specially designed for the space in my wall. I will consider the match providential, but not intelligently designed in the sense of design advocates.
Likewise, I do not remember any of Behe's examples as being something required by every living organism. Half of a flagellum may be useless (or it may not-who knows?), but it is not deadly.
Dr. David Campbell
Saint Mary's College of Maryland
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