Isaac Newton’s Personal Life

Especially in the earlier part of his life, Newton was a deeply introverted character and fiercely protective of his privacy. Even in his maturity, having become rich, famous, laden with honours and internationally acclaimed as one of the world’s foremost thinkers, he remained deeply insecure, given to fits of depression and outbursts of violent temper, and implacable in pursuit of anyone by whom he felt threatened. The most famous example of this is his carefully-orchestrated campaign to destroy the reputation of Gottfried Leibniz, who he believed (quite unfairly) had stolen the discovery of calculus from him. Yet he was also capable of great generosity and kindness, and there is no lack of tributes to his affability and hospitality, at least in his later years.

His psychological problems culminated in what would now be called a nervous breakdown in mid-1693, when, after five nights of sleeping ‘not a wink’, he temporarily lost all grip on reality and became convinced that his friends Locke and Pepys were conspiring against him. He later confessed to Locke that during this crisis, ‘when one told me you were sickly ... I answered twere better if you were dead’ (it is not clear whether Newton really did tell anyone this or merely imagined that he had). He seems, however, to have made a full recovery by the end of the year.

Many post-Freudian biographers (and not only fully paid-up Freudians) trace the roots of Newton’s insecurity and aggressiveness to his earliest years. His father died before he was born. When he was barely three years old, his mother remarried and moved into the home of her new husband Barnabas Smith, leaving the infant Isaac in the care of her own parents until Smith’s death some seven years later, when she came back, bringing with her two daughters and a son from her second marriage.

It should be said that such an arrangement was not particularly unusual in the mid-seventeenth century, but that does not in itself rule out the possibility - if not the likelihood - that this early experience of loss and betrayal permanently damaged Newton’s capacity for trust and close friendship. It has also been suggested - though this is purely conjectural and much disputed - that he was a repressed homosexual, which if true would undoubtedly have placed a man of his background and upbringing under extreme mental strain.

Whatever the reasons, the fact remains that Newton’s defensive secretiveness makes it extremely difficult to form a full and balanced assessment of his character. There are no private diaries, and hardly any of his correspondence touches on details of his private life or state of mind. Though we are lucky to have a substantial collection of second- and third-hand accounts of Newton’s early years (see the documents in Newton as Seen by Others), only a very few manuscripts in his own hand, dating from his boyhood and undergraduate years, give a more direct insight into his personal world.

By far the most important of these is the list Newton wrote out in 1662 of all the sins he could remember having committed, which he kept up-to-date for an uncertain but fairly short period thereafter (in the Fitzwilliam Notebook). Addressed directly to God, this gives a fascinating glimpse into Newton’s conscience. Perhaps the most striking feature of the list is how short it is and how innocuous most of the ’sins’ now seem. The misdemeanours Newton confessed are far less racy than those recorded in Samuel Pepys’s much more famous and substantial diary, but they obviously weighed heavily on him, and he adopted the same strategy as Pepys of writing in shorthand as a sort of code (though in both cases it is a relatively simple code to crack).

It says much about the sternly puritanical cast of Newton’s upbringing that many years after the event he still felt guilty about several minor instances of Sabbath-breaking, including ‘Squirting water on Thy day’ and ‘Making pies on Sunday night’. Other misdeeds seem, to modern secular ears, even more innocuous: ‘Idle discourse on Thy day and at other times’; ‘Peevishness at Master Clarks for a piece of bread and butter’. Yet there are also hints of the rages and dark depressions that would continue to blight his adult life: ‘Striking many’; ‘Punching my sister’; ‘Wishing death and hoping it to some’.

Nothing else quite so revealingly personal as this survives, but much can be read between the lines of the other private notebooks Newton kept as a schoolboy and undergraduate.

In the Pierpont Morgan Notebook, begun probably in 1659 (two years before Newton went to Cambridge), there are numerous series of words arranged, under a number of subject headings, in quasi-alphabetical order. This was done, presumably, as a handwriting and/or vocabulary-building exercise, and for the most part the lists are copied verbatim from a popular text-book of the day, Francis Gregory’s Nomenclatura brevis anglo-Latino, but Newton makes some surprising and surely revealing additions of his own. The word ‘Father’, copied from Gregory, is followed by Newton’s own supplement ‘Fornicator, Flatterer’, while ‘Brother’, though it is indeed followed by ‘Bastard’ in Gregory’s list, sparked a whole volley of further abusive terms in Newton’s mind, including ‘Blasphemer’, ‘Brawler’, ‘Babler’, ‘Babylonian’, ‘Bishop’ and ending with ‘Benjamite’. A ‘Benjamite’ was an over-indulged youngest son (in reference to Genesis 42, in which Jacob shows his youngest son Benjamin preferential treatment over his brothers). It is surely significant that Newton’s younger half-brother was also called Benjamin.

The other most crucial evidence for an understanding of Newton’s development in adolescence and adulthood is supplied by the lists of expenses he kept from 1659-69 in the Fitzwilliam Notebook and another one now known as the Trinity Notebook. These soften the image of an unsmiling, self-absorbed, Puritan Newton by revealing that as an undergraduate he did get out once in a while, to the tavern and the bowling green, and even occasionally played cards (and lost). Perhaps still more surprisingly, he appears to have run an informal money-lending operation for fellow students at Cambridge, though whether he charged interest on his loans is unclear.

These notebooks also chart the development of Newton’s intellectual interests. His practical bent, which later enabled him to devise and conduct experiments unassisted and to build most of his scientific apparatus himself, is already evident in the Pierpont Morgan notebook, the early part of which is crammed with recipes for making paints and medicines and instructions for performing conjuring tricks. In 1669, the expense lists begin to fill up with purchases of (al)chemical materials, books and equipment to stock the private laboratory he set up in the grounds of Trinity College. His disillusion with the very conservative curriculum on offer at Cambridge is evidenced by another notebook (Add. Ms. 3996 in Cambridge University Library), which begins with a series of notes on Aristotle and other orthodox academic sources but then abruptly changes tack and engages actively with the latest theories in science and mathematics, particularly those of Descartes.

Newton’s intellectual activities as an undergraduate were almost entirely extra-curricular. His near-total disregard for the subjects he was ostensibly supposed to be studying - primarily the ethics and natural philosophy of Aristotle - actually led to his being regarded as a decidedly poor scholar until his genius was recognised by the mathematics professor Isaac Barrow. But as this notebook proves, he was in fact far more in touch with current developments in international scholarship than most of his tutors and professors.

Unfortunately, no such personal material survives - if it ever existed - from the later, more public phase of Newton’s career. But the insights these documents offer into his formative years, adolescence and early adulthood make them indispensable to any attempt to form a rounded picture of Newton the man.

© 2024 The Newton Project

Professor Rob Iliffe
Director, AHRC Newton Papers Project

Scott Mandelbrote,
Fellow & Perne librarian, Peterhouse, Cambridge

Faculty of History, George Street, Oxford, OX1 2RL -

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