“Many of these mystics, by following what they were taught by some treatises, secretly preserved from one generation to another, achieved discoveries which would not be despised even in our modern days of exact sciences.
Roger Bacon, the friar, was laughed at as a quack, and is now generally numbered among “pretenders” to magic art; but his discoveries were nevertheless accepted, and are now used by those who ridicule him the most. Roger Bacon belonged by right if not by by fact to that Brotherhood which includes all those who study the occult sciences.
Living in the thirteenth century, almost a contemporary, therefore, of Albertus Magnus and Thomas Aquinas, his discoveries – such as gunpowder and optical glasses, and his mechanical achievements – were considered by every one as so many miracles. He was accused of having made a compact with the Evil One.”
H. P. Blavatsky
The Mark Of God: Understanding Your "I AM Presence" 