Probably in adolescence, he went to Paris & studied in the universities there. His prior education, as a child, must have been extensive, for even upon his arrival he was as well-grounded in the Latin & Greek classics as any of his peers. By the middle 1240's he was lecturing in Paris & was respected as an instructor there. He had studied under, & taught alongside, many great intellectuals of his day, such as Alexander of Hales & William d'Auvergne.
By the late 1240's he started spending a great deal of money & time on elaborate experiments, training assistants, & collecting rare books & arcane tomes. He also cultivated relationships with a wide array of intellectuals, both within & outside the faculty & student-body of Oxford. For this reason, he gained a reputation as something of an eccentric, and never really shook this reputation off, for the rest of his life.
Among the things he did in his laboratory were devising the camera obscura, or the use of a pinhole to observe a solar eclipse. He studied the flight of birds with their flapping wings. He made a number of astronomical observations. He studied light and rainbows & conducted a vast number of experiments & observations on optics & the bending of light.
As much as Bacon experimented, many of his experiments proved fruitless, & furthermore, he engaged in a great deal of speculation, which he never got around to confirming by experiment. He came up with a formula for gunpowder, & while he speculated that it could be used to construct weapons, he never actually did so (cannon & guns would be invented a century later). He speculated that, since hot air rose, it could be contained, such that a vehicle could float in the air and move about without touching the ground. He speculated on how to make mechanically-powered vehicles. He suggested that lenses could be used to correct poor vision (spectacles — which actually came into use during his lifetime).
Occasionally, though, he would release a letter or treatise covering some topic, then be reprimanded for doing so by the Order. At least a few of these brief works got around, however, & in 1266, Pope Clement IV mentioned the "wondrous philosophical works of the friar Bacon" to someone else. Somehow, either directly or through gossip, one or more of his treatises had come to the Pope's attention, & the Pope assumed it was part of a much larger body of work that Bacon had set down.
Suddenly, Bacon had a goal: to do what the Pope thought he had already done! He became reclusive & even elusive, during this time, fearing what the Order might do if they discovered what he was working on (even if he could claim it was for the Pope's benefit). By the end of 1267, he had written Opus majus (the "Greater Work"), Opus minus (the "Lesser Work"), and Opus tertium (the "Third Work"). He sent these on to the Pope.
Within these works, Bacon expounded on his fundamental ideas: that education ought to be rooted in the physical, the tangible, the observable, the measurable; that curriculum should center on languages, as well as metaphysical disciplines, especially mathematics, geometry, alchemy, and optics (a field which he, himself, had opened up immensely, & which was the much-talked-about technology of the time). While theology & other esoteric disciplines — he never advocated abandoning them — they should only play a secondary role in education. Studying metaphysical disciplines, experimenting & observing, opened the mind of the student, in ways that esoteric disciplines could not, & it was this opening of the mind which enhanced one's knowledge.
Clement was impressed with Bacon, as were many in the universities of Europe. But Clement died in 1268, & the sorts of curricular reforms that Bacon had advocated, never came to pass.
For a time the Franciscan Order let up on him, & he resumed some of his experimentation & speculation; for his work had reached the attention of the Pope, & they could hardly stand in his way.
When he started veering into mysticism, particularly ideas also advocated by Joachim di Fiore, the Order cracked down on him again — imprisoning him for a time in the late 1270's. (The exact time & length of his imprisonment is unknown.)
From this point on, he drifted in and out of obscurity, at times afraid to publish for fear of another crackdown by his Order, at other times motivated to speak out, no matter what, out of his strong conviction in his own ideas. Even so, many scholastics came to Oxford to study under him — he continued lecturing late into his life — and many sources claimed he was the pre-eminent scholar of his day. His reputation for brilliance never wavered, nor did his reputation for eccentricity.
This is, essentially, the basis of the "scientific method," which is: Observe nature; hypothesize cause & effect; observe or experiment to test hypothesis; revise hypothesis if needed; observe and/or experiment again to test hypothesis; etc. until a verifiable conclusion has been reached.
While we cannot precisely say that Bacon "invented" the scientific method, its foundations lay clearly in his three Opii. Furthermore, he practiced what he preached, & especially in the field of optics, in which he accomplished a great deal of work & innovation.
Also, while it appears that I'm giving a great deal of credit for the principle of learning by verification, this is not really the case. He was very much the product of his times, greatly influenced by his mentors (especially Grosseteste), his colleagues, & his students, as well as by the Latin & Greek classics, which he started reading as a child. He was simply an outspoken advocate for the metaphysical disciplines & the principle of verification. Others said much the same thing — & would do so, after him — but it would still take the rest of Europe a few centuries to absorb this concept & begin building modern science upon it.
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