The Mice once called a meeting to decide on a plan to free themselves of their enemy, the Cat. At least they wished to find some way of knowing when she was coming, so they might have time to run away. Indeed, something had to be done, for they lived in such constant fear of her claws that they hardly dared stir from their dens by night or day. Many plans were discussed, but none of them was thought good enough. At last a very young Mouse got up and said: “I have a plan that seems very simple, but I know it will be successful. All we have to do is to hang a bell about the Cat’s neck. When we hear the bell ringing we will know immediately that our enemy is coming.” All the Mice were much surprised that they had not thought of such a plan before. But in the midst of the rejoicing over their good fortune, an old Mouse arose and said: “I will say that the plan of the young Mouse is very good. But let me ask one question: Who will bell the Cat?”
More heat than light seems to me to be generated by the demand for IDists to “define CSI” and the equations that are fired back in response. Nobody is disputing that we have plenty of equations. Here is that bright young mouse, Dembski’s:
χ= –log2[10120 · φS(T)·P(T|H)]
The problem seems to me to lie in Belling the Cat.
So let’s take a closer look at that equation.
Dembski defines φS(T) as:
The number of patterns for which S’s semiotic description of them is at least as simple as S’s semiotic description of T
Where S is “a semiotic agent”. Fair enough. If a “semiotic agent” (me, you, Dembski, a visting Martian) spots a pattern that can be described simply enough, it is a candidate for CSI testing, whether it is a black monolith on the moon (“a black monolith”) faces on Mount Rushmore (“faces of American presidents”), or a sequence of nucleotides that results in a protein that helps an organism survive (“functional protein”), it’s a candidate.
However, it’s the next bit that presents the cat-belling problem, and it’s a problem, I suggest, with any of the definitions of CSI, or its various acronymic relatives, so far proffered: H.
To infer design, Dembski requires that we reject the “chance hypotheses, H“: In his Specification paper, Dembski suggests various examples of chance hypotheses, the rejection of which might lead us to conclude Design.
- that a coin is fair
- that an archer hit a small target by chance
- that a die is fair, and that the rolls are stochastically independent
All fine so far. But then:
- the relevant chance hypothesis that takes into account Darwinian and other material mechanisms
And there’s your belling problem, right there. Dembki’s entire solution to the problem of detecting design absolutely depends on the proper calculation of the distribution of probabilities under his null hypothesis. As he himself says:
We begin with an agent S trying to determine whether an event E that has occurred did so by chance according to some chance hypothesis H (or, equivalently, according to some probability distribution P(·|H)).
That is just fine, if you’ve got a nice tame cat, like a fair coin or die, and we simply want to know whether the coin or die is indeed fair, because we can define “fair” as a very specific probability distribution, because we have a perfectly good theorem. We can also compute a fairly good probability distribution for the landing points reached by arrows from a blind archer, either by empirical means, or by some kind of null model. But in the context of inferring design from biology, the probability distribution a “chance hypothesis that takes into account Darwinian and other material mechanisms” – is precisely what Darwin and evolutionary biologists spend their days trying to find out!
If ID proponents can calculate the probability distribution under a “chance hypothesis that takes into account Darwinian and other material mechanisms”, then, cool. Science will be done, and the Nobel committee can be disbanded.
But until they’ve done that, no matter how many equations they produce, they haven’t given us any definition of CSI that will allow us to detect design in biology, no matter how useful such definitions may be is for detecting nefarious design in seedy gaming houses, or whether an archer is peeking through a blindfold.
The cat remains unbelled.