LOGIC AND MEMORY IN LINNAEUS'S SYSTEM OF TAXONOMY.

SUMMARY. 1. The principles on which Linnaeus based his taxonomy are shown to be, at least in intention, primarily Aristotelian. 2. He, like others, was trying to produce a classification founded on the real natures of organisms, not on superficial resemblance; the method he adopted was to classify by the rules of Logical Division, which involve the determination of the essence of each entity. 3. Consequently his idea of a natural system was not that in use at the present; certain comments by historians of science are therefore incorrect. 4. A distinction is made between taxonomies of analysed and of unanalysed entities. Logical Division is appropriate only to the former. 5. Linnaeus's classificatory unit was the genus, not the species. His principles led him to assert that all genera must be distinct and natural; moreover, since they were stable units, however much the higher groups of a classification changed from author to author, he insisted that their names must be memorized. 6. Most of his rules of nomenclature follow directly from this requirement that the botanist must know and remember all genera. 7. The increase in knowledge of plants since Cesalpino had already led to the breakdown of at least one important theoretical grouping; in Linnaeus, the conflict between theoretical requirements and actual facts is very evident. Because of it, his practice often approached the modern when his theory did not. 8. It is suggested that the principles of Logical Division, unrecognized as such, may still be a powerful source of unwarranted bias in modern classifications.