Isaac Newton and Astrology

Witness for the Defence or for the Prosecution?

by Robert H. van Gent[1]

Introduction

From times immemorial, astrology has been a determining factor in the decisions and actions of men of all ranks and stations. At the begin of the 17th century, great scientists as Tycho Brahe, Galileo Galilei, Johannes Kepler and Pierre Gassendi – now best remembered for their roles in the development of modern physics and astronomy – all held astrology in high esteem.

However, at the end of the 17th century, the scientific community had completely turned away from astrology. For some the subject of derision, others preferred to ignore it completely – so, hardly a single word on astrology, either pro or contra, is to be found in the works of scientists as Christiaan Huygens (1629-1695)[2] or Isaac Newton (1642-1727).

However, in the case of Newton, the astrological literature presents a different view and even claims that Newton was in secret an ardent student of astrology.[3] As evidence the following anecdote is often quoted: when the astronomer Edmond Halley (1656-1742), of comet fame, once spoke depreciatively on the subject of astrology, Newton is said to have berated him with the remark: “Sir Halley, I have studied the matter, you have not!”

How much value may we store in such a testimony? The first questions that should be answered are: what is the source for this statement and what evidence is there that Newton ever “studied the matter”.

Portrait of Isaac Newton painted in 1689 by Sir Godfrey Kneller (Farleigh House, Farleigh Wallop, Hampshire)

The Evidence from Newton’s Writings

During the past few decades, an enormous amount of studies have been published on Newton, reaching a high-water mark during the tercentenary of the publication of Newton’s Philosophiæ naturalis principia mathematica(1687). Many of his hitherto unpublished papers, notably those from the so-called ‘Portsmouth Collection’, have been edited and commented on.

However, none of these studies have turned up one shred of evidence that Newton ever conducted any research on astrology.[4] One of the foremost Newton scholars, the English historian of science Derek Thomas Whiteside has stated that he never found any reference to astrology among the 50 million words which have been preserved from Newton’s hand.[5]

Moreover, the claim that the Bodleian Library at Oxford possesses a rare treatise on astrology written by Newton has also proven to be completely unfounded.[6]

Newton’s Library

Corroborative evidence on how minimal Newton’s interests on astrology really were can be found by inspecting the inventory of the books from his library that was made up after his death. This inventory has been preserved and in many cases even the books themselves, with Newton’s own comments and annotations, have been traced to various major libraries.[7]

Among the 1752 books with identifiable titles on this list, no less than 477 (27.2%) were on the subject of theology, 169 (9.6%) on alchemy, 126 (7.2%) on mathematics, 52 (3.0%) on physics and only 33 (1.9%) on astronomy. Surprisingly, Newton’s books on the disciplines on which his scientific fame rests amount to no more than 12% of his library.

At his death, Newton’s library possessed no more than four books on the subject of astrology: a work by the German astrologer Johann Essler from Mainz (end 15th/begin 16th century),[8] a treatise on palmistry and astrology by the English doctor/astrologer Richard Saunders (1613-1675),[9] an almanac from the same using the pseudonym Cardanus Rider[10] and finally a work debunking astrology by the philosopher-poet and Cambridge professor Henry More (1614-1687).[11]

Newton’s Initiation into Science

Ironically, Saunder’s book on palmistry and astrology may even have been the incentive to Newton’s scientific career. On August 31, 1726, shortly before his death, Newton was interviewed by his nephew John Conduitt (1688-1737), who was collecting biographical material on his illustrious uncle.

During this interview, Newton confided to Conduitt that his interest in science had first been roused in the summer of 1663, when, as a young student at Cambridge, he purchased a book on astrology[12] at the midsummer fair at Stourbridge. Baffled by the incomprehensible astrological diagrams and calculations in this work he then studied some books on geometry and calculus (such as by Euclid, Frans van Schooten and René Descartes) and was “soon convinced of the vanity & emptiness of the pretended science of Judicial astrology”.[13]

Conduitt’s notes are also corroborated by another memorandum that was drawn up shortly after Newton’s death by his friend Abraham de Moivre (1667-1754) and which was also consulted by Conduitt.[14] Although the Newton biographer Louis Trenchard More[15]expressed his reservations against the trustworthiness of an anecdote recorded more than 60 years after the event, it is cited as completely reliable in the more authoritative Newton biographies by David Brewster[16] and Richard Samuel Westfall.[17]

Portrait of Edmond Halley painted around 1687 by Thomas Murray (Royal Society, London)
click for a larger image

Newton’s Secret Investigations

The studies into Newton’s unpublished papers mentioned above have revealed that during the greater part of his scientific career, his secret passions in fact lay in alchemy[18] and matters of theology (such as the nature of the Holy Trinity, the dimensions of Solomon’s Temple, biblical prophecies and biblical chronology).[19]

It will therefore not come as a surprise that the true source for our anecdote in fact derives from Newton’s latter interests. More than 50 years ago the American historian of science I. Bernard Cohen[20] was able to trace it back to the highly regarded Newton biographies by the English physicist David Brewster (1781-1868) in which it is cited in full as:[21]

‘… when Dr. Halley ventured to say anything disrespectful to religion, he invariably checked him, with the remark, “I have studied these things – you have not”.’[22]

The fact that Halley and Newton often quarreled on theological matters is confirmed by another remark recorded by John Conduitt, who in turn heard it from his wife (and Newton’s niece) Catherine Conduitt (née Barton; 1679-1739).[23] However, these altercations were never so intense as to cause a rift between these two great scientists.

http://www.staff.science.uu.nl/

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