Opus Majus

The Opus Majus, or "Greater Work," is Roger Bacon's most significant work, written in Medieval Latin at the request of Pope Clement IV. Completed in 1267, it spans 878 pages, covering a wide range of natural sciences, including grammar, logic, mathematics, physics, and philosophy. Bacon also produced two shorter works, Opus Minus and Opus Tertium, to complement his major treatise.

The text is divided into seven parts: the first identifies obstacles to wisdom, such as reliance on unreliable authorities; the second explores the relationship between philosophy and theology, asserting theology's foundational role in all sciences. The third part examines Biblical languages—Latin, Greek, Hebrew, and Arabic—and their importance for understanding divine wisdom. Part four focuses on mathematics, where Bacon critiques the Julian Calendar and observes shifts in equinoxes. Optics are discussed in part five, drawing from Arab scholars like Alhazen, covering vision, light refraction, and optical instruments.

Part six delves into experimental science, touching on alchemy, gunpowder, celestial bodies, and futuristic inventions like microscopes and flying machines. The final section addresses moral philosophy and ethics. A 1733 publication by William Bowyer omitted the seventh part, highlighting incomplete availability of Bacon's work.

Recent scholarship underscores Bacon's religious dedication to the Franciscan Order, framing Opus Majus as a reformist plea amid apocalyptic expectations, aimed at enhancing missionary training and defending Christianity against adversaries.