Roger Bacon: Quotes about knowledge

“Mathematics is the gate and key of the sciences. … Neglect of mathematics works injury to all knowledge, since he who is ignorant of it cannot know the other sciences or the things of this world. And what is worse, men who are thus Ignorant are unable to perceive their own ignorance and so do not seek a remedy.”

Roger Bacon book Opus Majus

cited in: Morris Kline (1969) Mathematics and the physical world. p. 1
Opus Majus, c. 1267

Men , World , Mathematics , Knowledge

“For the things of this world cannot be made known without a knowledge of mathematics.”

Roger Bacon book Opus Majus

Cited in: Opus majus: A translation by Robert Belle Burke. Vol 1 (1962). p. 128
Opus Majus, c. 1267
Context: For the things of this world cannot be made known without a knowledge of mathematics. For this is an assured fact in regard to celestial things, since two important sciences of mathematics treat of them, namely theoretical astrology and practical astrology. The first … gives us definite information as to the number of the heavens and of the stars, whose size can be comprehended by means of instruments, and the shapes of all and their magnitudes and distances from the earth, and the thicknesses and number, and greatness and smallness, … It likewise treats of the size and shape of the habitable earth … All this information is secured by means of instruments suitable for these purposes, and by tables and by canons.. For everything works through innate forces shown by lines, angles and figures.

World , Mathematics , Knowledge

“If in other sciences we should arrive at certainty without doubt and truth without error, it behooves us to place the foundations of knowledge in mathematics…”

Roger Bacon book Opus Majus

Bk. 1, ch. 4. Translated by Robert B. Burke, in: Edward Grant (1974) Source Book in Medieval Science. Harvard University Press. p. 93
Opus Majus, c. 1267

Truth , Error , Mathematics , Knowledge

“The conquest of learning is achieved through the knowledge of languages.”

Roger Bacon

Source: The Opus Majus of Roger Bacon - Volume 1

Knowledge , Learning

“I use the example of the rainbow and of the phenomena connected with it, of which sort are the circle around the sun and the stars, likewise the rod lying at the side of the sun or of a star which appears to the eye in a straight line… called the rod by Seneca, and the circle is called the corona, which often has the colors of the rainbow. But neither Aristotle nor Avicenna, in their Natural Histories, has given us knowledge of things of this sort, nor has Seneca, who composed a special book on them. But Experimental Science makes certain of them. [The experimenter] considers rowers and he finds the same colors in the falling drops dripping from the raised oars when the solar rays penetrate drops of this sort. It is the same with waters falling from the wheels of a mill; and when a man sees the drops of dew in summer of a morning lying on the grass in the meadow or the field, he will see the colors. And in the same way when it rains, if he stands in a shady place and if the rays beyond it pass through dripping moisture, then the colors will appear in the shadow nearby; and very frequently of a night colors appear around the wax candle. Moreover, if a man in summer, when he rises from sleep and while his eyes are yet only partly opened, looks suddenly toward an aperture through which a ray of the sun enters, he will see colors. And if, while seated beyond the sun, he extend his hat before his eyes, he will see colors; and in the same way if he closes his eye, the same thing happens under the shade of the eyebrow; and again, the same phenomenon occurs through a glass vessel filled with water, placed in the rays of the sun. Or similarly if any one holding water in his mouth sprinkles it vigorously into the rays and stands to the side of the rays; and if rays in the proper position pass through an oil lamp hanging in the air, so that the light falls on the surface of the oil, colors will be produced. And so in an infinite number of ways, as well natural as artificial, colors of this sort appear, as the careful experimenter is able to discover.”

Roger Bacon book Opus Majus

6th part Experimental Science, Ch.2 Tr. Richard McKeon, Selections from Medieval Philosophers Vol.2 Roger Bacon to William of Ockham
Opus Majus, c. 1267

Books , Color , Way , History

“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

Nature , Knowledge , Science , Perfection

“Argument is conclusive… but… it does not remove doubt, so that the mind may never rest in the sure knowledge of the truth, unless it finds it by the method of experiment. For if any man who never saw fire proved by satisfactory arguments that fire burns, his hearer's mind would never be satisfied, nor would he avoid the fire until he put his hand in it that he might learn by experiment what argument taught.”

Roger Bacon

Cited in: Carol A. Dingle (2000) Memorable Quotations: Philosophers of Western Civilization. p. 21

Truth , Knowledge , Learning

“There are in fact four very significant stumbling blocks in the way of grasping the truth, which hinder every man however learned, and scarcely allow anyone to win a clear title to wisdom, namely, the example of weak and unworthy authority, longstanding custom, the feeling of the ignorant crowd, and the hiding of our own ignorance while making a display of our apparent knowledge.”

Roger Bacon

Cited in: John H. Woodburn, Ellsworth Scott Obourn (1965) Teaching the pursuit of science. p. 70

Wisdom , Truth , Way , Feeling

“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

Wisdom , Women , War , Books