The Linnaean system is so well established that we can hardly imagine an alternative, but before Linnaeus, systems of classification were often highly whimsical. Animals might be categorized by whether they were wild or domesticated, terrestrial or aquatic, large or small, even whether they were thought handsome and noble or of no consequence. Buffon arranged his animals by their utility to man. Anatomical considerations barely came into it. Linnaeus made it his life's work to rectify this deficiency by classifying all that was alive according to its physical attributes. Taxonomy — which is to say the science of classification — has never looked back.

It all took time, of course. The first edition of his great Systema Naturae in 1735 was just fourteen pages long. But it grew and grew until by the twelfth edition — the last that Linnaeus would live to see — it extended to three volumes and 2,300 pages. In the end he named or recorded some 13,000 species of plant and animal. Other works were more comprehensive — John Ray's three-volume Historia Generalis Plantarum in England, completed a generation earlier, covered no fewer than 18,625 species of plants alone — but what Linnaeus had that no one else could touch were consistency, order, simplicity, and timeliness.