Part of the Third Work (Opus Tertium)

INTRODUCTION

I. On the causes of human ignorance.
II. On the connection of philosophy with theology.
III. On the usefulness of the study of languages.
IV. On the usefulness of mathematics:
1. In praise of mathematics.
2-4. On physical forces and their subjection to mathematical laws.
[5]. The application of mathematics to sacred subjects, including astronomical judgments original: "judicia astronomiae"; refers to the use of astronomy for predictions and calculations and the correction of the calendar original: "correctio calendarii".
[6]. The application of mathematics to political matters, divided into a treatise on Geography and a treatise on Astrology.
V. On the science of optics.
VI. On experimental science.
VII. On moral philosophy.

All these are printed in Bridges' edition, except the last two (fifth and sixth) divisions of Part VII, which are missing.

After finishing the Great Work original: "Opus Majus", Bacon was moved to compose the Lesser Work original: "Opus Minus" by the following considerations: (1) a single work might be lost during travel: (2) the many responsibilities of the Pope made a short summary and an easier explanation of many difficulties desirable: (3) some matters had been forgotten in the first work and could be inserted in the second: (4) "having found remedies for earlier difficulties I could add some necessary things which I was not able to insert before." This is a mysterious statement which perhaps refers to the alchemical treatises term: alchemy; the medieval study of transforming matter, often focused on creating gold or finding a universal medicine included in the Lesser Work.¹

The Great Work and the Lesser Work, together with the treatise On the Multiplication of Species original: "De multiplicatione specierum"; Bacon's work on the physics of light and influence and a separate treatise on Alchemy, were sent to the Pope by the hand of John, the favorite pupil of Roger Bacon.²

The same reasons which led Bacon to write the Lesser Work next led him to undertake the Third Work original: "Opus Tertium",³ with

¹ Opus Tertium, edited by Brewer, pages 5, 42, 43: compare page 77 below.
² The same work, pages 3, 227, 230: edited by Duhem, pages 164, 183 (corresponding to pages 61, 82 below). (Compare Compendium of Study original: "Comp. Studii", edited by Brewer, page 414.)
³ Opus Tertium, edited by Brewer, page 67.