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Logical trees and the tree of Darwin

The basis for treelike classifications in general is ultimately Aristotle’s logic of division, the diairesis, which was the common heritage of the West before science. But it does not follow that naturalists who began biological classification were explicitly following Aristotle’s logical principles. 
The conflation of logical and biological species by the modern proponents of what has come to be known as the Essentialism Story has implications for both the nature of biological essentialism, and also for the use of logical trees by taxonomists. It is my claim that taxonomists in natural history and subsequently in biology always had a peculiar notion of taxa that was distinct from the logical and metaphysical notions in philosophy, and one cannot draw conclusions from critiques of the latter to the former, although as it happens the reverse direction leads to some insights in logic and metaphysics.
Even when logical trees such as the Tree of Porphyry or Ramus were discussed by those who also did biology, such as George Bentham, this did not materially affect their use of classificatory trees in the least.
Taxonomy was never done in biology by the method of per genus et differentium. Darwin's metaphor of the tree of evolution is an explanation the classification practices that arose from Linnaeus that could be represented as a tree, but these did not arise from logical trees.


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