Name: Opus Tertium
Author: Roger Bacon

“The strongest argument proves nothing so long as the conclusions are not verified by experience.”
[H]aec vocatur scientia experimentalis, quae negligit argumenta, quoniam non certificant, quantumcunque sint fortia, nisi simul adsit experientia conclusionis. Et ideo haec docet experiri conclusiones nobiles omnium scientiarum, quae in aliis scientiis aut probantur per argumenta, aut investigantur per experientias naturales et imperfectas...

Roger Bacon book Opus Tertium

OQHI, 43 http://www.mlat.uzh.ch/MLS/text.php?tabelle=Rogerus_Baco_cps4&rumpfid=Rogerus_Baco_cps4,%20Opus%20tertium,%20%2013&level=3&corpus=4&lang=0&current_title=Opus%20tertium&links=&inframe=1&hide_apparatus= as cited in: James J. Walsch (1911) """"Science at the Medieval Universities"""" in: Popular Science, May 1911, p. 449 http://en.wikisource.org/wiki/Page:Popular_Science_Monthly_Volume_78.djvu/459
Opus Tertium, c. 1267
Context: The strongest argument proves nothing so long as the conclusions are not verified by experience. Experimental science is the queen of sciences, and the goal of all speculation.

“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”

Roger Bacon book Opus Tertium

Source: Opus Tertium, c. 1267, Ch. 14 as quoted in J. H. Bridges, The 'Opus Majus' of Roger Bacon (1900) Vol.1 http://books.google.com/books?id=6F0XAQAAMAAJ Preface pp.x-xi
Context: All these foregoing sciences 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 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.

“But I did not work all that much, since in the pursuit of Wisdom this was not required.”

Roger Bacon book Opus Tertium

OQHI, 65 http://www.mlat.uzh.ch/MLS/text.php?tabelle=Rogerus_Baco_cps4&rumpfid=Rogerus_Baco_cps4,%20Opus%20tertium,%20%2020&corpus=4&lang=0&current_title=Opus%20tertium&links=&inframe=1 as cited in: Jeremiah Hackett (2009) """" Roger Bacon http://plato.stanford.edu/archives/win2012/entries/roger-bacon"""" in: The Stanford Encyclopedia of Philosophy. Edward N. Zalta (ed.)
Opus Tertium, c. 1267
Context: I have labored much in sciences and languages, and I have up to now devoted forty years [to them] after I first learned the Alphabetum; and I was always studious. Apart from two of these forty years I was always [engaged] in study [or at a place of study], and I had many expenses just as others commonly have. Nevertheless, provided I had first composed a compendium, I am certain that within quarter or half a year I could directly teach a solicitous and confident person whatever I know of these sciences and languages. And it is known that no one worked in so many sciences and languages as I did, nor so much as I did. Indeed, when I was living in the other state of life [as a Magister], people marveled that I survived the abundance of my work. And still, I was just as involved in studies afterwards, as I had been before. But I did not work all that much, since in the pursuit of Wisdom this was not required.

“And this [experimental] science verifies all natural and man-made things in particular, and in their appropriate discipline, by the experimental perfection, not by arguments of the still purely speculative sciences, nor through the weak, and imperfect experiences of practical knowledge. And therefore, this is the matron of all preceding sciences, and the final end of all speculation.”
Et hæc scientia certificat omnia naturalia et artificialia in particulari et in propria disciplina, per experientiam perfectam; non per argumenta, ut scientiæ pure speculativae, nec per debiles et imperfecta experientias ut scientiae operativæ. Et ideo hæc est domina omnium scientiarum præcedentium, et finis totius speculationis.

Roger Bacon book Opus Tertium

Ch 13 ed. J. S. Brewer Opera quadam hactenus inedita (1859) p. 46
Opus Tertium, c. 1267

“One man I know, and one only, who can be praised for his achievements in this science. Of discourses and battles of words he takes no heed: he follows the works of wisdom, and in these finds rest. What others strive to see dimly and blindly, like bats in twilight, he gazes at in the full light of day, because he is a master of experiment. Through experiment he gains knowledge of natural things, medical, chemical, indeed of everything in the heavens or earth. He is ashamed that things should be known to laymen, old women, soldiers, ploughmen, of which he is ignorant. Therefore he has looked closely into the doings of those who work in metals and minerals of all kinds; he knows everything relating to the art of war, the making of weapons, and the chase; he has looked closely into agriculture, mensuration, and farming work; he has even taken note of the remedies, lot casting, and charms used by old women and by wizards and magicians, and of the deceptions and devices of conjurors, so that nothing which deserves inquiry should escape him, and that he may be able to expose the falsehoods of magicians. If philosophy is to be carried to its perfection and is to be handled with utility and certainty, his aid is indispensable. As for reward, he neither receives nor seeks it. If he frequented kings and princes, he would easily find those who would bestow on him honours and wealth. Or, if in Paris he would display the results of his researches, the whole world would follow him. But since either of these courses would hinder him from pursuing the great experiments in which he delights, he puts honour and wealth aside, knowing well that his wisdom would secure him wealth whenever he chose. For the last three years he has been working at the production of a mirror that shall produce combustion at a fixed distance; a problem which the Latins have neither solved nor attempted, though books have been written upon the subject.”

Roger Bacon book Opus Tertium

Bridges assumes that Bacon refers here to Peter Peregrinus of Maricourt.
Source: Opus Tertium, c. 1267, Ch. 13 as quoted in J. H. Bridges, The 'Opus Majus' of Roger Bacon (1900) Vol.1 http://books.google.com/books?id=6F0XAQAAMAAJ Preface p.xxv

“I have labored much in sciences and languages”

Roger Bacon book Opus Tertium

OQHI, 65 http://www.mlat.uzh.ch/MLS/text.php?tabelle=Rogerus_Baco_cps4&rumpfid=Rogerus_Baco_cps4,%20Opus%20tertium,%20%2020&corpus=4&lang=0&current_title=Opus%20tertium&links=&inframe=1 as cited in: Jeremiah Hackett (2009) """" Roger Bacon http://plato.stanford.edu/archives/win2012/entries/roger-bacon"""" in: The Stanford Encyclopedia of Philosophy. Edward N. Zalta (ed.)
Opus Tertium, c. 1267
Context: I have labored much in sciences and languages, and I have up to now devoted forty years [to them] after I first learned the Alphabetum; and I was always studious. Apart from two of these forty years I was always [engaged] in study [or at a place of study], and I had many expenses just as others commonly have. Nevertheless, provided I had first composed a compendium, I am certain that within quarter or half a year I could directly teach a solicitous and confident person whatever I know of these sciences and languages. And it is known that no one worked in so many sciences and languages as I did, nor so much as I did. Indeed, when I was living in the other state of life [as a Magister], people marveled that I survived the abundance of my work. And still, I was just as involved in studies afterwards, as I had been before. But I did not work all that much, since in the pursuit of Wisdom this was not required.