PREFACE.

operations with which moral or political science is concerned. This science is the mistress of every department of philosophy. It employs and controls them for the advantage of states and kingdoms. It directs the choice of men who are to study in sciences and arts for the common good. It orders all members of the state or kingdom so that none shall remain without his proper work.'

The seventh part of the Opus Majus Latin: "Greater Work," Bacon's massive 13th-century encyclopedia of the sciences. is for the first time printed in this edition. Unfortunately it is not complete. It consisted, as we learn from the fourteenth chapter of the Opus Tertium Latin: "Third Work," an introductory summary Bacon sent to the Pope., of six divisions; and the only two MSS. An abbreviation for manuscripts—hand-written copies of the text from the medieval period. of it as yet discovered, those of Dublin and Oxford (the first of which, as will be shown afterwards, is copied from the second), stop short before the conclusion of the fourth. We gather, however, that the missing portions are not of primary importance.

Another alteration of considerable importance has been made in the present edition. Professor Émile Charles, in his very important monograph on Roger Bacon (Bordeaux, 1861), pointed out that the treatise De Multiplicatione Specierum Latin: "On the Multiplication of Species," a technical work by Bacon regarding how physical forces, like light or heat, spread through space., which in Jebb's Samuel Jebb (1694–1772) was the physician and scholar who produced the first major printed edition of the Opus Majus in 1733. edition of the Opus Majus is placed between the fifth and sixth sections of the work, does not in reality belong to it. And indeed the second sentence of the treatise makes this evident. "It must be remembered," original Latin: "Recolendum est" Bacon observes, "that in the third part of this work it was touched upon that essence, substance, nature, power, potency, virtue, and force signify the same thing." original Latin: "quod in tertia parte hujus operis tactum est quod essentia, substantia, natura, potestas, potentia, virtus, vis, significant eandem rem." No such passage is to be found in any part of the Opus Majus, least of all in the third part, which deals with Comparative Philology The study of how languages develop and relate to one another.. Here again the Opus Tertium comes to our aid. Several references will be found there to a distinct treatise sent to Pope Clement IV simultaneously with the Opus