Little known fact about Isaac Newton: far from being a no-nonsense scientist disdainful of superstition and the occult, Newton was actually heavily steeped in esoteric lore and Hermetic thought. One might think of him as being both the last of the magicians and the first of the scientists.
To begin with, it seems that Newton had certain connections with Freemasonry. In 1703, around the time he had been elected President of the Royal Society, he became friends with a French Protestant refugee named Jean Desgauliers, who was later to become one of the most influential figures in the spread of the Craft throughout Europe in the 18th Century. While there is no record of Newton himself being a Freemason, he had been a member of a quasi-Masonic society called the Gentlemen's Club of Spalding, whose other members included such notables as Alexander Pope, and further, some of his works and attitudes reflect prevalent Masonic thought of the time. For instance, he esteemed Noah more than Moses as the ultimate source of all esoteric knowledge. In 1689 he embarked on what he himself considered to be his most important work (even more than what posterity would think of as his most important, the Principia Mathematica Philosophiae Naturalis), The Chronology of Ancient Kingdoms Amended. This work was a historical study of ancient monarchies that attempted to establish the origins of the institution of kingship as well as the importance of Israel over all other ancient kingdoms. Furthermore, Newton believed that ancient Judaism had been a repository of divine knowledge, much of which had been lost, corrupted, suppressed, or diluted over thousands of years. He believed that some of these divine secrets had filtered down to Pythagoras, whose notions about the "music of the spheres" he believed were a metaphor for the law of gravitation he is credited with formulating. In order to establish a precise chronology for dating events in scripture and mythology, he used Jason's quest for the Golden Fleece as a pivotal event, and interpreted it, as did many other Masonic thinkers of the time, in alchemical terms. He attempted to find Hermetical correspondences between music and architecture. And like all Masons, he was obsessed with the Temple of Solomon, believing that hidden within the dimensions and configuration of the structure were secret alchemical formulas and the ancient rituals performed there involved alchemical processes.
Newton was also a deeply religious person, and was obsessed with the search for natural correspondences and the laws of nature. This led him, apart from formulating the Theory of Gravity and the Laws of Motion, into a study of numerology and sacred geometry. Newton was also a close friend of Robert Boyle, who suffered a fate similar to Newton at the hands of modern scientific historians, as he is remembered to be the ultimate debunker of alchemy when he was actually its greatest exponent at the time. Newton and John Locke had inherited Boyle's papers after his death in 1691, and Newton is also known to have practiced alchemy actively. His personal library included annotated copies of the Rosicrucian manifestos, and hundreds of works on alchemy, including a work by Nicolas Flamel, which he is said to have copied entirely by hand.
And there's more: Newton was also vehemently opposed to the idea of a Holy Trinity, and questioned the divinity of Jesus, collecting all works that discussed the subject he could find. He also disliked the fashionable Deism of the time, although he is widely believed today to be one of their number, which is blatantly untrue. He could not accept the idea of the cosmos being a vast machine and of God as the celestial engineer who put it all into motion. He further believed that the New Testament was not completely authentic, but rather that some passages were corruptions created by vested interests in the 5th century.
These kinds of preoccupations and interests lend credence to the theory that Newton may in fact have been at one time Grand Master of that mysterious secret society known as the Prieure de Sion.