(Carl von Linné). Born May 23, 1707, in Råshult; died Jan. 10, 1778, in Uppsala. Swedish naturalist. Member of the Paris Academy of Sciences (1762). Known for his system for naming plants and animals.

Linnaeus, the son of a country pastor, studied the natural sciences and medicine at the universities of Lund (1727) and Uppsala (from 1728). In 1732 he journeyed throughout Lapland; the botanical results of his journey were recorded in Florula Lapponica (1732; complete edition under the title Flora Lapponica, 1737). In 1735, Linnaeus moved to the city of Hartecamp in Holland, where he managed a botanical garden; in that same year he defended his doctoral thesis, “A New Hypothesis of Intermittent Fevers.” In 1735 he also published his book Systema naturae (12 editions were published during his lifetime). In 1738, Linnaeus began to practice medicine in Stockholm; in 1739 he headed the naval hospital there and obtained the right to dissect corpses to determine causes of death. He helped to organize the Royal Swedish Academy of Sciences, becoming its first president in 1739. Beginning in 1741, Linnaeus held chairs at the University of Uppsala, where he taught medicine and the natural sciences. He promoted the broad introduction of the natural sciences into the curriculum of the university.

Linnaeus’ system for classifying plants and animals was the crowning achievement of the great work of early 18th-century botanists and zoologists. One of his most important contributions was the introduction and use of binomial nomenclature in Systema naturae. According to this system, each species is designated by two Latin names—the generic and the specific. Linnaeus’ determination of the concept of species was based on morphological (resemblance within the bounds of the progeny in a single family) and physiological (the presence of fertile progeny) criteria. He established a precise coordination of systematic categories: class, order, genus, species, and variety.

In his plant classification, Linnaeus placed major emphasis on the number, size, and arrangement of the stamens and pistils in the flower, as well as on the monoecious, dioecious, or polyoicous character of the plant. He believed that the reproductive organs were the most essential and permanent parts of plants. On the basis of this principle he divided all plants into 24 classes. Owing to the simplicity of the nomenclature Linnaeus used, descriptive work became considerably easier and species acquired precise characteristics and names. Linnaeus himself discovered and described approximately 1,500 species of plants.

Linnaeus divided all animals into six classes: mammals, birds, amphibians, fishes, worms, and insects. The class of amphibians included amphibians and reptiles, and the class of worms, all forms of invertebrates known in his time except insects. One of the merits of this classification was that man was included in the system of the animal kingdom and assigned to the class of mammals and order of primates.

The classifications of plants and animals proposed by Linnaeus are artificial from a modern point of view, since they were based on a small number of arbitrarily assumed characteristics and do not reflect the true kinships between different forms. Thus, on the basis of only one common character—the structure of the bill—Linnaeus assigned the ostrich, cassowary, peacock, and chicken to the same order. Recognizing the artificiality of his system, he attempted unsuccessfully to construct a “natural” system based on an aggregate of many characteristics.

An opponent of the idea of historical development of the organic world, Linnaeus believed that the number of species remains constant and that from the moment of their “creation” the species had not changed. Therefore, the task of systematics was to reveal the order in nature that was established by the “creator.” However, Linnaeus’ extensive experience and his familiarity with plants from various habitats could not help but shake his metaphysical ideas. In his last works, Linnaeus very cautiously expressed the proposition that all species of a single genus originally constituted one species, and in like manner he admitted the possibility of the appearance of new species, formed as a result of the crossbreeding of already existing species.

Linnaeus also classified soils and minerals, human races, and diseases (according to symptoms). In addition he discovered the poisonous and healing properties of many plants. He wrote a number of works, most of which are on botany and zoology; some of his writings deal with medical theory and practice, such as Materia medica (Medicinal Substances, vols. 1–3, 1749–63), Genera morborum (Types of Diseases, 1763), and Clavis medicinae duplex (Double Key to Medicine, 1766).

Linnaeus’ library, manuscripts, and collections were sold by his widow to the British botanist J. Smith, who in 1788 founded the Linnaean Society in London. Today the society is one of the most important scientific centers.