W. James King's study positions William Gilbert's De magnete (1600) not as a clean break with medieval thought but as a modification of older traditions. King, a curator at the Smithsonian, draws on the absence of quantification in Gilbert's work—noting that historians like Koyré, Whitehead, and Cassirer saw measurement as marking the shift to modern science—to question Gilbert's role as a founder. Instead, King compares Gilbert's explanations of the loadstone with those from the Middle Ages and earlier, arguing that Gilbert can best be understood as a modifier of the old.

Gilbert's Aristotelian Framework

King shows that Gilbert retained key Aristotelian concepts while reworking them. For Gilbert, the earth is an element with a natural motion—magnetic coition—just as fire naturally moves upward. The substantial form of his element, pure loadstone, acts through magnetic qualities, a direct parallel to Aristotelian elemental forms acting through hot, dry, etc. Gilbert also adopts the idea of a proper place for each element, but redefines it magnetically. This framework, King argues, makes Gilbert's system a transformation of medieval natural philosophy rather than a rejection of it.

The Earth as a Magnetic Body

King emphasizes Gilbert's radical move: endowing the earth itself with magnetic powers, which medieval philosophers attributed to heavenly bodies. In Gilbert's system, the earth's magnetic form causes rotation, holds it together, and aligns all magnetic materials. King notes that Gilbert extends this to other celestial bodies—each star and planet has its own unique form causing parts to conform and revolve. The sun's form is superior, ordering planetary orbits; the moon governs tides. This hierarchy of forms, King observes, allows the loadstone to acquire its powers from the earth, a causal chain rooted in Gilbert's cosmology.

Magnetic Forces and Their Limits

King details Gilbert's account of magnetic force: it emanates in all directions but is bounded by an orbis virtutis, whose shape follows the stone's. The poles are the 'thrones' of magnetic powers, yet verticity is strongest at the equator. Strength depends on shape and mass—a bar magnet concentrates force more than a sphere. King notes Gilbert's claim that a loadstone has a maximum force that cannot be increased, though weaker ones can be strengthened by stronger. These specifics, drawn from the excerpts, show Gilbert's systematic, if non-mathematical, approach to magnetism.

King's Method and Evidence

King builds his argument by juxtaposing Gilbert's statements with medieval sources, though the excerpts only hint at this comparison. He cites historians like Koyré and Whitehead to frame the issue of quantification, then uses Gilbert's own terminology—'coition,' 'orbis virtutis,' 'thrones'—to demonstrate the Aristotelian inheritance. The excerpts show King relying on Gilbert's text directly, quoting phrases such as 'the substantial form of his element, pure loadstone, acts through the magnetic qualities.' This close reading allows King to trace conceptual continuity without claiming Gilbert's work is merely derivative.

King's essay rewards readers who attend to the specific language Gilbert uses—'coition,' 'orbis virtutis,' 'thrones'—and who consider how King frames each concept as a transformation of earlier ideas. The excerpts provide a clear sense of King's thesis, but the full text likely includes more extensive medieval comparisons. For a first reading, focus on how King uses Gilbert's own terms to build his case for continuity rather than revolution.