Joseph Glanvill was a skeptic, a prominent defender of the experimental research of the early Royal Society, a liberal rationalistic Anglican theologian and preacher, and a staunch and influential believer in witchcraft. He studied at Cambridge, where he came under the influence of Henry More. On first learning of René Descartes's work Glanvill became an advocate of Cartesianism but was quickly led to cast doubt on it as a metaphysical theory because of More's objections. He then treated Cartesianism as a working hypothesis and began analyzing how much certitude anyone could have about what is going on in the world. He came into contact with John Wilkins, the bishop of Chester, and began developing his case in terms of the categories employed by him.

Glanvill's first work, The Vanity of Dogmatizing (1661), was soon revised into the larger Scepsis Scientifica (1665), and began with a most...