How religious was Isaac Newton?

Isaac Newton was the greatest scientist in history, and his discoveries of the laws of motion and universal gravitation provided a vivid example of the power of reason to grasp the nature of reality.  This example served as inspiration for the thinkers of the 18th-century Enlightenment. The Enlightenment philosophes subjected religion to an unprecedented rational scrutiny, many of them rejecting Christianity for deism and a few even turning to atheism.

Given this chain of events, it was natural for many to assume that Newton could not have been very religious; after all, he was the Enlightenment's exemplar of reason. But it turns out that Newton thought about religion a great deal, and his private manuscripts on theology are voluminous, totaling four million words. It has been only in the past century that Newton's religious writings have been examined in depth, and this has yielded a significantly better understanding of Newton's beliefs.

Newton accepted many of the conventional religious beliefs of the English Puritan culture in which he was raised: "Newton trusted the Bible [except for certain "corruptions"] and often took it literally, especially prophetic texts from Daniel and Revelation. He believed in predestination, the bodily resurrection of Jesus, the future resurrection of the faithful, and the millennial kingdom ruled by Christ." (Davis, p. 118) He even calculated a possible starting date for the events of the Apocalypse: the year 2060 AD.

After discovering the universal law of gravitation, Newton did not believe that the gravitational attraction of bodies is a power inherent in matter. He saw the bodies as controlled by God's will or God's agent.

There are also elements in Newton's manuscripts which suggest something more rational in his approach to religion, which led to his rejection of several church doctrines.  Newton had contempt for what he called superstition and the worship of the mysterious:  "It is the temper of the hot and superstitious part of mankind in matters of religion ever to be fond of mysteries, and for that reason to like best what they understand least."  (quoted in Westfall, p. 193)

The Christian doctrine that was most disturbing to Newton was the Trinity — the idea that God is three persons (the Father, the Son, and the Holy Ghost) who are all fully God, while at the same time there is only one God. This struck Newton as superstitious and irrational. He believed that there is simply one God, along with various subordinates. Jesus was God's son, and had a special divine status, but Jesus was not God. Newton came to the conclusion that Christianity — and the Bible itself — had been corrupted by the supporters of the Trinity in the early Christian church.  He worked exhaustively to identify the specific Biblical passages that he considered fraudulent.

For Newton to make public his rejection of the Trinity would have been illegal in 17th-century England (and would have, at the very least, destroyed his university career), so he shared his religious writings and opinions with only a few close friends.

One fact that clearly emerges from Newton's religious writings is his active-minded approach. Newton was not content to simply accept official Church teachings as the truth. He had to examine them; he had to read and master the Bible for himself; he had to study Church history for himself. He had to decide which church doctrines he agreed with and which he did not. As one biographer has pointed out, the manuscripts "reveal a Newton who spent his entire adult life probing, questioning ... the received notion of Christianity." (Westfall p. 229)

What is the significance of Newton's belief in religion?

Does it prove that science and religion are fundamentally compatible?  No.

It does prove that great scientific work can be done by men who also have strong religious beliefs. But they have to keep their religion out of their science. Newton's published books on physics contain no religious arguments for his scientific conclusions, and mentions of God in these books are few and far between.

Why did Newton keep his religion out of his physics? He accepted an idea popular in the 17th century: the idea of God's two books — the book of Scripture and the book of Nature — and the necessity of keeping them separate. Newton advised that "Religion and Philosophy are to be preserved distinct. We are not to introduce divine revelations into Philosophy, nor philosophical opinions into religion." (Manuel, p. 28)

This division comes ultimately from Thomas Aquinas, with his distinction between the truths of reason and truths of faith. But that is a subject for another blog post.

References

The Religion of Isaac Newton: The Freemantle Lectures 1973, Frank E. Manuel, Oxford, Clarendon Press, 1974.

"Isaac Newton", entry in Encyclopedia of Science and Religion, by Stephen Snobelen, 2003 [link]

"A Time and Times and the Dividing of Time: Isaac Newton, the Apocalypse and 2060 AD", Stephen D. Snobelen, Canadian Journal of History, Dec. 2003

"Myth 13: That Isaac Newton's Mechanistic Cosmology Eliminated the Need for God", Edward B. Davis, pp. 115-122 of Galileo Goes to Jail: and Other Myths about Science and Religion, edited by Ronald L. Numbers, Harvard University Press, Cambridge, MA, 2009

"The Rise of Science and the Decline of Orthodox Christianity: A Study of Kepler, Descartes, and Newton", Richard S. Westfall, pp. 218-237, God and Nature: Historical Essays on the Encounter between Christianity and Science, ed. David C. Lindberg and Ronald L. Numbers, University of California Press, Berkeley, 1986

Science and Religion in Seventeenth-Century England, Richard S. Westfall, Univ of Michigan Press, 1973