In this and the following chapters, we look at methods of classification. This chapter is historical; Chapter 7 takes up the story with phenetics and cladistics and concerns controversy as well as method. Chapters 8-10 are also much concerned with taxonomic controversy. Throughout we shall be looking at the concept of a “Natural Classification”. As we saw in Chapter 2, naturalness up to the time of Linnaeus was often taken to inhere in the correct use of method. In order to show how this came about, I shall spend some time discussing the method of logical division as developed by Plato and Aristotle and eventually transformed into the taxonomic method used by Linnaeus. Another characterization of naturalness was as the “plan of creation” which developed with “rational morphology” and the homology concept (Chapter 4). Finally, with the acceptance of evolution, some sort of relationship to phylogeny was taken to be the criterion, but, as we shall see in this chapter, it did not lead to any standardised taxonomic method for nearly a hundred years.

The method of logical division

In Chapter 2 (Section II), we noticed an early example of the so-called method of division, which appears in The Sophist, a later work of Plato. In The Sophist, Plato takes the art of angling and demonstrates its properties by making it one of the “taxa” in the lowest rank of a dichotomous dendrogram of the Arts (Fig. 2.3). This was an early version of the type of classificatory pattern that later appears as the tree of Porphyry, the Stufenreihe, and the “Hennigian comb”.