Opus Majus of Roger Bacon, Vol. I (Bridges ed.)

method, though essential, is insufficient. It must be supplemented by the method of experiment. Even a purely geometrical proof is not convincing or conclusive, until the execution of the diagram has enabled us to add ocular, that is to say, experimental, evidence that the demonstration is sound. This method, moreover, will lead us into new regions into which mathematical procedure is not able to penetrate. Experimental science governs all the preceding sciences (domina est omnium scientiarum praecedentium it is the mistress of all preceding sciences), it controls their methods; in prosecuting its own special researches it makes use of their results.

Here then ends the Opus Majus as presented in the edition of 1733. A glance at the fourteenth and preceding chapters of the Opus Tertium The Third Work, in which the structure and purpose of the Opus Majus are reviewed, will show how disastrously the suppression of the seventh section of the work has mutilated it. 'All these foregoing sciences,' says Bacon, 'are, properly speaking, speculative. There is indeed in every science a practical side, as Avicenna teaches in the first book of his Art of Medicine. Nevertheless; of Moral Philosophy alone can it be said that it is in the special and autonomatic sense practical, dealing as it does with human conduct with reference to virtue and vice, beatitude and misery. All other sciences are called speculative: they are not concerned with the deeds of the present or future life affecting man's salvation or damnation. All procedures of art and of nature are directed to these moral actions, and exist on account of them. They are of no account except in that they help forward right action. Thus practical and operative sciences, as experimental alchemy and the rest, are regarded as speculative in reference to the