Design evidence # 2piR : circular logic

Holmes:

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While a person can use homology to build a theory of evolutionary development (creating a model to explain what is seen), one cannot then say "look at the similarity of these things, that proves evolution is true."

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Totally correct. This is the fundamental argument (now mostly resolved, afaik) between the old systematists who were basically assuming ancestry from similarity, and then assuming phyletic evolution from the inferred ancestry! IOW, the systematists assumed the lineage and then constructed the trees. The reason I say it has been mostly resolved is that the science of cladistics starts with relationships of derived characteristics, not inferred ancestry. Here's a fairly easy-to-read overview: Basics of Cladistic Analysis that takes you step by step through the process.Basically, sonnike isn't far off (although out of date by at least 25 years) - the old-style systematists HAD got themselves into the bind where evolution was inferred from an inferred ancestry which was used as evidence of evolution... Doesn't mean, of course, that anyone still does this. One more example of creationist projection - they assume simply because anything any theist has ever written is utterly unchangeable, they assume that science operates the same way.

I agree that it hasn't changed the taxonomy - although a few lineages have been re-sorted. The argument was about epistemology, not classification. I think it came down to assuming evolution vs inferring evolution from relationships based on derived characteristics (synapomorphies). Cladists claim their approach is "purer", and that they could derive evolutionary relationships from the data, rather than going from what was supposed to be an a priori assumption. To be honest, it's almost too esoteric an argument for me to follow closely. A cladist would rather be boiled in oil than claim a particular organism represented an ancestor. Like I said, most of this was resolved a quarter century ago.