Barry seems to have noticed TSZ again, and so I will take this opportunity of inviting him over here, where he can post freely, and will not be banned unless he posts porn or malware or outs someone, which I expect he can manage not to do.
And he responds to my post, Lawyers and Scientists. He does so in two parts, so I will devote two posts to them. Here is my response to his first part. Barry writes:
First Liddle writes that I have
. . . confused the assumption of common descent with the conclusion of common descent, and thus detected circular reasoning where there is none.
Where did I do such a thing? Boiling that paragraph down I made the following claims:
- Common descent is not necessarily false.
- But Cladistics does not establish common descent one way or the other.
- Instead, cladograms are constructed ASSUMING common descent.
- It is circular reasoning to conclude that a technique establishes that which it assumes in the first place.
- Therefore, anyone who says that cladistics establishes the fact of common descent has used faulty reasoning and is mistaken.
- There are in fact people who make that mistake.
To establish beyond doubt point 6, Glen Davidson kindly jumps into Liddle’s own combox with this:
Barry: “This is not to say that common descent is necessarily false; only cladistics does not establish the matter one way or the other.”
Glen: “Of course it does. What a ridiculously ignorant dweeb.”
All six assertions seem to me to be on solid ground. Not only are they true, they are not even controversial. But for Liddle’s charge to be correct, at least one of the points I made must be false. OK Liddle, which of the six totally non-controversial points I have made do you disagree with? If the answer is “none,” then the only gracious thing to do is to withdraw your claim.
The short answer is that I disagree with 2-6, for the reasons I gave in my first post: the answer lies in null hypothesis testing. Far from “assuming a tree”, both linear correlations and tree distributions are tested by FITTING a slope/tree, and testing whether the best fit is a better fit than would be expected under the NULL of no linear relationship/no underlying tree structure. If, having fitted the slope/tree, the fit is no better than would be expected under the null of no linear relationship/no underlying nested hierarchy, then you RETAIN THE NULL. If it is better, i.e. if a fit as good as that observed is UNLIKELY under the null, you reject the null and consider your hypothesis (linear fit; common descent pattern) supported. Of course there could reasons other than common descent that could explain the tree – but the tree can be established as an OBSERVATION to be EXPLAINED. Which Linnaeus did before Darwin. And it was that clear tree that Darwin sought to explain by, firstly, Common Descent, and, secondly, by a mechanism that would explain adaptive change-over-time.
If Barry cannot understand that testing a NULL HYPOTHESIS is the OPPOSITE of assuming that your model is true, then perhaps he could shoot an email to the former owner of his site.
It is of course true that null hypothesis testing is counter-intuitive and doesn’t do what many of its practitioners think it does, but it’s still an excellent workhorse, and what’s more, is the beating heart of ID’s very own eleP(T|H)ant.
[My response to the second part will have to wait – I have some null hypotheses to test first….]
ETA: Looks like this response deals with Pt II at as well.