Part of the Third Work (Opus Tertium)

INTRODUCTION.

On 22 June, 1266, Clement IV, who had been elected Pope on 5 February, 1265, wrote to Friar Roger Bacon of the Order of Minors. He thanked Bacon for his letter and for the oral original: "vivâ voce" explanations provided by "our beloved son G. called Bonecor, a knight" original: "miles".¹ "In order," the Pope continues, "that we may better understand your meaning, we command you by apostolic writings, despite the order of any superior to the contrary or any constitution of your Order, to send to us as soon as possible a fair copy of that work which we asked you to communicate to our beloved son Raymond de Laon before we became Pope. You must also explain to us by letter the remedies you think advisable for the dangers you lately pointed out. You shall do this without delay and as secretly as you can."

In answer to this command, Roger Bacon composed the Great Work original: "Opus Majus", for the Pope was wrong in thinking that the work was already written. The Great Work goes by various names: the Great Work, the First Work original: "Opus Primum", or the Principal Work original: "Principale". These distinguish it from the Lesser Work original: "Opus Minus", also called the Second Work original: "Opus Secundum", and from the Third Work original: "Opus Tertium". It was also called the Preliminary Treatise original: "Tractatus præambulus" to distinguish it from the Principal Writing original: "Scriptura principalis". This latter was an encyclopedic work on all the sciences which Bacon hoped to write but never completed. In the text of the work itself, Bacon usually refers to it as "this persuasion" original: "haec persuasio". Throughout the text, he emphasizes the practical usefulness of knowledge in a way likely to appeal to a man of the world.

The Great Work consists of the following seven parts of unequal length:

¹ Bliss, in the Calendar of Papal Registers, volume I, page 420, reads "Bone Cornules" instead of "Bonecor the knight" original: "Bonecor miles".