Ray was the son of the village blacksmith in Black Notley and attended the grammar school in nearby Braintree. In 1644, with the aid of a fund that had been left in trust to support needy scholars at the University of Cambridge, he matriculated at one of the colleges there, St. Catherine's Hall, and moved to Trinity College in 1646. Ray had come to Cambridge at the right time for one with his talents, for he found a circle of friends with whom he pursued anatomical and chemical studies. He also progressed well in the curriculum, taking his bachelor's degree in 1648 and being elected to a fellowship at Trinity the following year; during the next 13 years he lived quietly in his collegiate cloister.

Ray's string of fortunate circumstances ended with the Restoration. Although he was never an excited partisan, he was thoroughly Puritan in spirit and refused to take the oath that was prescribed by the Act of Uniformity. In 1662 he lost his fellowship. Prosperous friends supported him during the subsequent 43 years while he pursued his career as a naturalist.

That career had already begun with the publication of his first work in 1660, a catalog of plants growing around Cambridge. After he had exhausted the Cambridge area as a subject for his studies, Ray began to explore the rest of Britain. An expedition in 1662 to Wales and Cornwall with the naturalist Francis Willughby was a turning point in his life. Willughby and Ray agreed to undertake a study of the complete natural history of living things, with Ray responsible for the plant kingdom and Willughby the animal.

The first fruit of the agreement, a tour of the European continent lasting from 1663 to 1666, greatly extended Ray's first-hand knowledge of flora and fauna. Back in England, the two friends set to work on their appointed task. In 1670 Ray produced a Catalogus Plantarum Angliae (“Catalog of English Plants”). Then in 1672 Willughby suddenly died, and Ray took up the completion of Willughby's portion of their project. In 1676 Ray published F. Willughbeii . . . Ornithologia (The Ornithology of F. Willughby . . .) under Willughby's name, even though Ray had contributed at least as much as Willughby. Ray also completed F. Willughbeii . . . de Historia Piscium (1685; “History of Fish”), with the Royal Society, of which Ray was a fellow, financing its publication.

Ray had never interrupted his research in botany. In 1682 he had published a Methodus Plantarum Nova (revised in 1703 as the Methodus Plantarum Emendata . . . ), his contribution to classification, which insisted on the taxonomic importance of the distinction between monocotyledons and dicotyledons, plants whose seeds germinate with one leaf and those with two, respectively. Ray's enduring legacy to botany was the establishment of species as the ultimate unit of taxonomy. On the basis of the Methodus, he constructed his masterwork, the Historia Plantarum, three huge volumes that appeared between 1686 and 1704. After the first two volumes, he was urged to compose a complete system of nature. To this end he compiled brief synopses of British and European plants, a Synopsis Methodica Avium et Piscium (published posthumously, 1713; “Synopsis of Birds and Fish”), and a Synopsis Methodica Animalium Quadrupedum et Serpentini Generis (1693; “Synopsis of Quadrupeds”). Much of his final decade was spent on a pioneering investigation of insects, published posthumously as Historia Insectorum.

In all this work, Ray contributed to the ordering of taxonomy. Instead of a single feature, he attempted to base his systems of classification on all the structural characteristics, including internal anatomy. By insisting on the importance of lungs and cardiac structure, he effectively established the class of mammals, and he divided insects according to the presence or absence of metamorphoses. Although a truly natural system of taxonomy could not be realized before the age of Darwin, Ray's system approached that goal more than the frankly artificial systems of his contemporaries. He was one of the great predecessors who made possible Carolus Linnaeus' contributions in the following century.

Nor was this the sum of his work. In the 1690s Ray also published three volumes on religion. The Wisdom of God Manifested in the Works of the Creation (1691), an essay in natural religion that called on the full range of his biological learning, was his most popular and influential book. It argued that the correlation of form and function in organic nature demonstrates the necessity of an omniscient creator. This argument from design, common to most of the leading scientists of the 17th century, implied a static view of nature that was distinctly different from the evolutionary ideas of the early and mid-19th century. Still working on his Historia Insectorum, John Ray died at the age of 77.