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Sir Isaac Newton
(25 Dec 1642 - 20 Mar 1727)

English physicist and mathematician who made seminal discoveries in several areas of science, and was the leading scientist of his era.


Isaac Newton
“The cause of gravity is what I do not pretend to know”

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by Frits Ahlefeldt (source)
“You sometimes speak of gravity as essential and inherent to matter. Pray do not ascribe that notion to me, for the cause of gravity is what I do not pretend to know, and therefore would take more time to consider of it.”
— Isaac Newton
From Letter to Richard Bentley (1693).

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This quote is from Newton’s correspondence with theologian Richard Bentley, who in 1692 delivered a series of sermons on the subject of “A Confutation of Atheism from the Origin and Frame of the World” at St. Martin-in-the-Field. This course of lectures was the first on the evidence of Christianity established by a bequest from Robert Boyle.

In preparing his sermons, Bentley had received Newton’s recommendations, in July 1691, for background information from parts of the Principia which had been published about five years earlier. After Bentley gave his oral presentations, but before publishing them, he consulted with Isaac Newton in several letters, clarifying a number of points regarding gravity and cosmogony, so that he could be sure the printed version of his lectures gave a correct interpretation of Newton’s ideas.

In Newton’s first reply (10 Dec 1692), he made his deep religious belief clear in his opening:

“When I wrote my treatise about our Systeme I had an eye upon such Principles as might work with considering men for the beleife of a Deity & nothing can rejoyce me more then to find it usefull for that purpose But if I have done the publick any service this way 'tis due to nothing but industry & a patient thought.”

Later in that same letter, Newton referred to the planets and their moons (the secondary planets):

“To your second Query I answer that the motions which the Planets now have could not spring from any naturall cause alone but were imprest by an intelligent Agent … its plaine that there is no naturall cause which could determin all the Planets both primary & secondary to move the same way & in the same plane without any considerable variation. This must have been the effect of Counsel.”

Bentley may have sent copies of the oral lectures to Newton (of which only one letter from Bentley survives). In one of these lost letters, it seems Newton felt his own views on gravity were somewhat misrepresented, so at the end of his second letter (17 January 1692/3) to Bentley about the lectures, Newton makes clear that he denies knowing gravity's cause:

“You sometimes speak of gravity as essential & inherent to matter: pray do not ascribe that notion to me, for ye cause of gravity is what I do not pretend to know, & therefore would take more time to consider of it.”

Within his fourth reply to Bentley, Newton included more on his view of gravity, in which he uses the word “immaterial” in the sense of being spiritual, rather than physical (material):

“Gravity must be caused by an agent [acting] consta[ntl]y according to certain laws, but whether this agent be material or immaterial is a question I have left to the consideration of my readers.”

In Hylarie Kochiras, Force, Matter, and Metaphysics in Newton's Natural Philosophy (2008), 173, footnote, the following summary of the exchange of letters is given, together with an explanation of the “1692/3” date notation. Links have been added to online transcripts of the letters from Newton:

The chronology of events (omitting mention of those letters of Bentley's that are not extant) is as follows.
November, 1692: Bentley delivers some version of what is later published as his 7th Lecture.
December 5, 1692: Bentley delivers some version of what is later published as his 8th Lecture.
December 10, 1692: Newton's first letter to Bentley.
January 17, 1692/3: Newton's second letter to Bentley, asserting that gravity is not essential to matter.
February 11, 1692/3: Newton's third letter to Bentley.
February 18, 1692/3: Bentley's letter to Newton, containing an “abstract and thread” of his then-unpublished Seventh Boyle Lecture.
February 25, 1692/3: Newton's fourth letter to Bentley, containing his remarks about matter acting without mediation.
1693: The published versions of Bentley's lectures appear.
1756: Newton's letters to Bentley are first published, as Four Letters from Sir Isaac Newton to Doctor Bentley.
 
The letters written during January and February are written with a slash between the years 1692 and 1693 because of change in custom for marking the new year. According to an older tradition, the new year did not begin until March 25th, with the Feast of the Annunciation. The newer practice, ushered in with the change from the Julian to the Gregorian calendar (a change made in England in 1752), was to take January 1st as the beginning of the new year. Documents written during the transitional period before this new custom had fully taken hold, and between January 1 and March 25th, are often dated with a slash between the years.

Text by Webmaster, with subject quote from Newton's second letter to Richard Bentley (17 Jan 1692/3). Collected in Four Letters From Isaac Newton to Doctor Bentley, Containing Some Arguments in Proof of a Deity, (1756), 20. The other quotes appear on pages 1, 5 and 25. (source)


See also:
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Nature bears long with those who wrong her. She is patient under abuse. But when abuse has gone too far, when the time of reckoning finally comes, she is equally slow to be appeased and to turn away her wrath. (1882) -- Nathaniel Egleston, who was writing then about deforestation, but speaks equally well about the danger of climate change today.
Carl Sagan Thumbnail Carl Sagan: In science it often happens that scientists say, 'You know that's a really good argument; my position is mistaken,' and then they would actually change their minds and you never hear that old view from them again. They really do it. It doesn't happen as often as it should, because scientists are human and change is sometimes painful. But it happens every day. I cannot recall the last time something like that happened in politics or religion. (1987) ...(more by Sagan)

Albert Einstein: I used to wonder how it comes about that the electron is negative. Negative-positive—these are perfectly symmetric in physics. There is no reason whatever to prefer one to the other. Then why is the electron negative? I thought about this for a long time and at last all I could think was “It won the fight!” ...(more by Einstein)

Richard Feynman: It is the facts that matter, not the proofs. Physics can progress without the proofs, but we can't go on without the facts ... if the facts are right, then the proofs are a matter of playing around with the algebra correctly. ...(more by Feynman)
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