Evolutionists complain that positive arguments for ID are lacking, and that all ID offers are negative arguments against evolution. Without granting all of that, I want to address whether there is something wrong with arguing for ID by arguing against evolution. I have done this before, but I’ve developed the argument further since then. This is adapted from a comment I posted on another thread earlier today.
I have argued in the past that there are only two possible explanations for biological origins on the table: either there was some intelligence guiding it, or there wasn’t. If the first is true, then some form of Intelligent Design is the right explanation. If not, then the only explanation on offer is unguided neo-Darwinian evolution (hereafter NDE).
At the end of the movie Expelled, Richard Dawkins speaks of the possibility that life on earth was designed, and opines that it might have been if the source of that design were some alien creatures. Many ID proponents found that a funny position for him to take, 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, at least, there is only one route up what he calls “Mount Improbable,” and that is the gradualistic road of natural selection acting on random variations.
So if he is right, then there are only two options on the table: Intelligent Design (in some form), or NDE. Now, these are dichotomous: if one is true, the other is false. Mainstream evolutionary scientists insist that NDE is fact, and that we know it is fact. One helpful way to express this certainty is to express it in terms of probabilities: p(NDE)=1 and p(ID)=0.
Because there are no other options on the table or even on the horizon, it would appear that the probability relationship must include only the terms stated so far here. That is, p(NDE) + p(ID)= 1. 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, then the probability of the other term decreases or increases by like measure.
ID theorists argue that certain features of the natural world are inconsistent with NDE. The Cambrian Explosion is one of them. It is hard to explain, strictly on NDE terms, how it came about. This is an example of a negative argument against NDE. This post is not about whether that 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 the binary relationship between ID and NDE, it must; for p(NDE) + p(ID)= 1. Suppose there is some merit to ID’s concerns about the Cambrian Explosion. The effect of that must be to reduce confidence in NDE by some non-zero amount. Supposing also that before this argument was made, the universal consensus was that p(NDE)=1. To the extent that the Cambrian Explosion argument has merit, that confidence would be reduced, and the result would be that p(NDE) < 1, and p(ID) > 0. (How much those probabilities change depends on how successful the argument actually is.) Confidence in ID (its increase in probability) would be numerically identical to the decrease in confidence in NDE, because the sum of the two probabilities must equal 1.
Thus a negative argument against NDE is a positive argument in favor of ID.
But when I have written of this before, some have objected to my considering only two possibilities: ID (in some form) and NDE. “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 NDE? How could we know that?”
We can deal with that this way. Let’s grant that there could be Unknown Possibilities, and call them UP. In that case we would have to say, p(NDE) + p(ID) + p(UP) = 1. That certainly ought to cover all the possible explanations.
There must be some number between 0 and 1 that expresses the probability of Unknown Possibilities — p(UP) — explaining biological origins. How shall we assign that probability? How slippery is that number? Does it always adjust to p(NDE), such that p(NDE) + p(UP) always equals 1? It seems to me some participants in this debate or so opposed to ID, that’s what they would insist: “ID is not the answer. If NDE turns out not to be the answer either, then there must be some other unguided, naturalistic explanation for life.” That’s equivalent to saying p(NDE) + p(UP) always equals 1, and p(ID) always equals 0.
But treating unknown possibilities that way is nothing more than a “no-design of the gaps” argument. It starts with ignorance with respect to the unknown possibilities and moves to an assumption that if NDE is not the answer, then UP is. It does so with no knowledge: “unknown” means unknown, after all. That’s not very impressive reasoning, and in fact I can’t think of any scientific or logical reason to accept it.
What if we take a more balanced view, then? What if we admit the possibility of UP, and we do so in a way that avoid the “no-design of the gaps” error. In that case the most reasonable way to proceed would be to assign p(UP) some more definite value, like, perhaps, 0.2. The number we choose really doesn’t matter, in view of the point I’m trying to make here, which is that a negative argument against NDE can be a positive argument for ID. We could simply call p(UP) an unknown constant and make the same argument we made above, adding K into the equation for that constant. My central point above remains identical to what it was before:
p(NDE) + p(ID) + K = 1. If the probability of either non-K term is 1, then the probability of the other is 0; if the probability of either term increases or decreases, then the probability of the other term decreases or increases by like measure. A negative argument against NDE is still a positive argument for ID.
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