Vernon Pratt

It has been claimed that in a single line of development the science of taxonomy stretches from Aristotle to the present day and that the Aristotelian 'essence' lies at the heart of much later thought about grouping. I try to establish some basic features of Aristotle's conception of 'essence', and then consider in more detail the conception of essence that entered into 18th century thought about classification, with a view to establishing discontinuities. 18th century thought, I note, has two kinds of essence, real and nominal, and I consider the view that a 'natural' classification in that context should be understood as one which is based on real essences. In place of this thesis, I advocate the view that the hidden foundation of 18th century systematics is a very restrictive articulation of the visual field which gives sense to the possibility of grouping according to the sum total of observable similarities and differences: and that it is this possibility that a 'natural' classification was conceived of as realising

The rationale for the common rejection of classical societal functionalism is that it entails treating a society as an intelligent purposer, capable of directing its own internal organization in furtherance of survival. But a more acceptable alternative account of the origins of a society's functional organization is conceivable: the individual unconsciously recognizes the needs of his group and directs his behaviour so that they are met. The plausibility of this explanation hangs on whether selection between groups occurs to any significant extent, however, and it is therefore on this question that the plausibility of classical societal functionalism itself depends.