Tom Gilson

The Evolutionists’ Complaint: It’s Wrong to Argue For ID By Arguing Against Evolution (Part 1 of 3)

Last week I posted an article in which I attempted to show that evidence against evolution can legitimately be evidence in favor of Intelligent Design. I ran into some serious opposition on that, and even though my interlocutors’ objections there were often mis-aimed, they did lead me to think through the matter more deeply. I got the argument wrong last time. I’m stating it here in a corrected form. I’ll borrow some of my wording from the previous version so that this article can stand alone, though I’m going to change terminology somewhat for clarity’s sake. This article divides naturally into three separate sections, so I am going to divide it into three posts published simultaneously. For those who followed the earlier discussion, there is some new material in this post, and I would draw your attention especially to the fifth through seventh paragraphs (counting this as number one). The second and third sections are quite different from what I posted previously.

The question is whether it is legitimate to regard evidence against evolution as evidence in favor of ID. Evolutionists often complain that positive arguments for ID are lacking, and that ID offers nothing but negative arguments against evolution. I’m going to refer to that as The Complaint. It is indeed true that ID makes part of its case (though certainly not all of it) on the basis of arguments against naturalistic evolution, so ID proponents must take The Complaint seriously. Is there something inherently wrong with ID arguing its case this way? Can a negative argument against evolution really be a positive argument for ID? Or is negative argumentation conceptually flawed from the start?

I’m going to begin with the simplest level of analysis and work upward from there to a fully realistic level. This argument becomes complex later on. I have placed a tree-diagram representing the whole of it at the end of the third post in this series. You may skip ahead and use it to guide you through if you like.

I begin by noting that at this time there are only two possible explanations for biological origins on the table: either some intelligence was guiding it, or there was no such intelligent guidance. If the first is true, then some form of Intelligent Design is the true explanation. If not, then the only explanation currently on offer is undirected random variation coupled with natural selection, which I will refer to here as Naturalistic Evolution, or NE.

At the end of the movie Expelled, Richard Dawkins speaks of the possibility that life on earth was designed, and opines that ID could explain earth’s life if the designers were some alien creatures. That raised some hearty chuckles from ID proponents, but in our laughter many of us missed what else he said: that those aliens, if they existed, must have come about by Darwinian processes. For Dawkins there is only one route up “Mount Improbable” (the term he used for life’s increasing complexity in his book The Blind Watchmaker). That one route is the gradualistic path of natural selection acting on random variations.

If he is in fact right about there being only one naturalistic route to biological complexity, then there are only two options open for consideration: Intelligent Design in some form (which of course is not an option Dawkins would consider), and NE. These are fully dichotomous: if one is true, the other is false, and vice-versa. Mainstream evolutionary scientists insist that NE is fact, and that we know it is fact. One helpful way to express their certainty is to express it in terms of probabilities: their view is that p(NE)=1 and p(ID)=0.

For this analysis I define evidence E for theory T as any information that, if true, increases the probability that T is true. I distinguish evidence from proof: it is that which adds to the probability of T, not that which proves T. Evidence is not unidimensional or unidirectional; there can be evidences for and against T, and each piece of evidence E must be considered in light of its own virtues and faults, in context of all other evidences for and against T. Further, there is a time factor factor involved. E is evidence for T if p(T) at T2 is greater after the introduction of E than at T1, before the introduction of E. This before/after relationship could be logical rather than chronological; whether E existed or was known at T1 is not as important as whether it was included in the probability analysis at T1.

There are many mainstream scientists who insist, as Michael Ruse has, that “Evolution is fact, FACT, FACT!” In other words, the matter has been settled, and regardless of any possible future evidence,  p(NE)=1. There is no possibility that ID is true: p(ID)=0. I can’t fathom how they can take that position. Evidence has to have some capability of influencing a theory, doesn’t it? Or is evolution true regardless of evidence? That’s hardly science.

Since “fact, FACT, FACT!” in that form is therefore fallacious reasoning and also bad science, I’ll proceed by entertaining the possibility that there is at least conceivably some evidence E that could reduce our confidence in evolution (even by the smallest fraction) such that  p(NE) < 1. That’s not assuming much. It’s a lot more reasonable than insisting that NE is true no matter what evidence might surface.

Now, if Dawkins is right that NE is the only possible naturalistic route up Mount Improbable, the probability equation for origins must include only the terms stated so far here; thus, p(NE) + p(ID)= 1. These are the only options on offer. If the probability of either term is 1, then the probability of the other is 0; if the probability of either term increases or decreases by some degree n, then the probability of the other term decreases or increases by n. 1 – p(NE) = p(ID), and 1 – p(ID) = p(NE).

ID theorists argue that certain features of the natural world are inconsistent with NE. The Cambrian Explosion is one of them. It is hard to explain on NE terms how it came about. This is an example of a negative argument against NE. This post is not about whether that argument is true or not; it is about whether, if there is merit to the argument, it counts legitimately as an argument in favor of ID.

And it seems to me that given a binary, dichotomous relationship between ID and NE, it must; for p(NE) + p(ID)= 1. Suppose for the sake of argument there is some merit to ID’s concerns about the Cambrian Explosion. The effect of that must be to reduce confidence in NE by some non-zero amount. Now suppose also that before this argument was presented, the universal consensus was that p(NE)=1. To the extent that the Cambrian Explosion argument has merit, confidence in NE must be reduced by some degree n, with the result that p(NE) = 1- n, and p(ID) = n. (The degree of change, n, depends on how successful the argument actually is.) Increased confidence in ID (its increase in probability) must be numerically identical to the decrease in confidence in NE, because the sum of the two probabilities must equal 1.

Therefore any evidence E that reduces the probability of NE as an explanation for origins increases the probability of ID as an explanation.

That brings us to the end of the first stage of this argument. To recap:

  1. The Complaint is that ID’s negative argumentation against NE is somehow illegitimate, unscientific, or otherwise weak or wrong.
  2. ID and NE are mutually exclusive.
  3. On Richard Dawkins’ view, NE is nature’s only available method for developing biological complexity.
  4. Therefore on that view, ID and NE fill the entire probability space for origins: p(NE) + p(ID)= 1.
  5. And therefore any successful negative evidence against NE is successful positive evidence for ID:

That is the simplest view of the argument, and it seems pretty cut-and-dried if random variation coupled with natural selection (NE) is nature’s only option for building biological complexity, as Dawkins thinks.

But when I have written of this before, some have objected to my considering only two possibilities: ID (in some form) and NE. “How do we know these are the only two possibilities?” they ask. “Science marches on, and who knows what we might discover? Why do we assume that ID is the only alternative to NE? How could we know that?”

That question takes us to the second section of this article.

Series Navigation (The Evolutionist's Complaint):<<< Arguing for ID By Arguing Against Evolution: Is It Legitimate?The Evolutionists’ Complaint: It’s Wrong to Argue For ID By Arguing Against Evolution (Part 2 of 3) >>>

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