Chapter 6 explores the progression of Joseph Glanvill’s membership of the Royal Society of London through an analysis of the Plus ultra (1668) and the following stream of texts in which he defends the Fellows’ work and discoveries against the attacks of Aristotelians, Galenists and university men. This examination focuses on Glanvill’s debates with Robert Crosse, a Puritan divine, and Henry Stubbe, a physician, as well as his relationships with several other Fellows of the Royal Society, particularly Henry Oldenburg and John Beale. Addressing these episodes allows the exploration of various contemporary responses to Glanvill, both positive and negative, and the impact these responses had on Glanvill’s reputation and that of the Society. Some of the responses discussed include those of Henry Oldenburg, John Beale, John Evelyn, Christopher Merrett and George Thomson. The relationship of this work to Sprat’s History of the Royal Society (1667) is also discussed. A broader perspective on this historiographically polarizing issue is provided by an analysis of the impact of Glanvill’s philosophical work in German-speaking lands, particularly through the correspondence of Gottfried Wilhelm Leibniz, German philosopher and mathematician; Jakob Thomasius, philosopher and jurist; and Georg Daniel Morhof, German writer and scholar.