Certain (largely unpublished) works of Isaac Newton included much that would now be classified as occult studies. He worked extensively outside the strict bounds of science and mathematics, particularly on chronology, alchemy, and Biblical interpretation (especially of the Apocalypse). Much of his writing on alchemy may have been lost in a fire in his laboratory, so the true extent of his work in this area may have been larger than is currently known. He also suffered a 'nervous breakdown' during his period of alchemical work, which is thought by some due to the psychological transformation that alchemy was originally designed to induce, though there is also speculation it may have been some form of chemical poisoning (possibly from mercury, lead, or some other substance).

Newton was also an astronomer, and as astrology and astronomy were one and the same for thousands of years leading up to and during Newton's time (think combination word: astrolomy), it is not illogical to suggest that he studied or at least dabbled in astrology. Astrology and alchemy had also been intertwined; conversely, Newton's study of mathematics was related to his breakthrough theories in gravity and astronomy, for which he is best known.

Since Isaac Newton was a well known alchemist of his time, and astrology and alchemy were and in some cases still are very closely linked, it is plausible that Newton had a very good working knowledge of astrology, or at the very least a basic understanding of astrological methodology as it was related to alchemy. Logically then, one would certainly have to know a good bit about astrology in order to use alchemy effectively, and Newton along with other prominent alchemists of his time definitely knew this.

It is, however, somewhat anachronistic to assume that the importance he attached to these is closely connected to contemporary attitudes. The work modern observers would call scientific were perhaps to him of lesser importance; Newton was a product of his time in that he still placed emphasis on rediscovering the occult wisdom of the ancients. In this sense, the common reference to the "Newtonian Worldview" as purely mechanistic is somewhat misguided, as John Maynard Keynes observed in 1942 after purchasing and studying Newton's alchemical works:

"Newton was not the first of the age of reason, he was the last of the magicians." -- John Maynard Keynes