The groundbreaking Principia Mathematica, Newton's breakdown and how to win at dice. Rebekah Higgitt (University of Kent) talks to us about the links between Samuel Pepys and Isaac Newton.

An earlier post on this blog looked at Pepys’s membership of the Royal Society, of which he was President for two years in 1684-6. “Arguably the most important event in the Royal Society’s history took place in this period”, it noted: the publication of Isaac Newton’s Principia Mathematica. This book, as the title in English explains, was a demonstration of the Mathematical Principles of Natural Philosophy, including Newton’s laws of motion and, most famously, universal gravitation. 
Isaac Newton's Principia Mathematica
Page from Newton's Principia Mathematica
Pepys’s name is printed in large type on the title page of the first edition, a copy of which has been loaned to the exhibition by the Royal Society. He is identified there as President of the Society, giving his and its imprimatur to authorise the publication on 5 July 1686, although the book was not in fact published until the following year. His role was, though, purely nominal: it was Edmond Halley, later second Astronomer Royal at Greenwich, who returned Newton’s thoughts to the question of gravitation, encouraged him to write and paid for the publication. 
It is, nevertheless, a great shame for biographers of Newton and historians of science that Pepys’s diary ended long before he became President of the Royal Society or had heard of Newton. Although they probably interacted little over the matter of Principia, we know that they became familiar and had common business to attend to. Probably the most significant example of the latter was the Royal Mathematical School at Christ’s Hospital. 
Bust of Isaac Newton at the National Maritime Musuem
Bust of Newton on display in the exhibition
Pepys was closely associated with the foundation of the School in 1673, along with Jonas Moore, the Surveyor General of the Ordnance who also took a key role in the foundation of the Royal Observatory. Its purpose was to provide a mathematical education to about 40 boys aged around 11 or 12 in preparation for a naval career. From the 1680s Newton’s advice was repeatedly sought with regard to the appointment of mathematical masters and on curriculum. Newton’s comments on the latter suggested significant ambition but perhaps poor understanding of what the boys could either cope with or would need. Pepys too believed that the scholars should be taught “with Method and Theory, able to informe and correct others” and not just practical matters and principles by rote, but they struggled to find the master who could deliver this over a two-year course. 
Badge of the mathematical scholars of Christ's Hospital
Badge of the mathematical scholars of Christ's Hospital
A more curious and dramatic incident occurred in the 1690s, which tells us something about the relationship between the two men and the circles in which they moved. In the summer of 1693 Newton suffered some sort of breakdown and a letter to Pepys on 13 September 1693 showed the extent of his anxiety and paranoia:
…I am extremely troubled at the embroilment I am in, and have neither ate nor slept well this twelve month, nor have my former consistency of mind. I never designed to get anything by your interest, nor by King James’s favour, but am now sensible that I must withdraw from your acquaintance, and see neither you nor the rest of my friends any more, if I may leave them quietly.
Pepys was concerned and asked a mutual acquaintance in Cambridge to check on Newton, who was then able to forward an apology. Around the same time Newton also apologised to John Locke for having accused him of trying “to embroil me wth woemen & by other means”, “thinking that there was a designe to sell me an office”, and wishing him dead. Newton’s paranoia seems to have concentrated on attempts to gain him a position in London but the cause of what was probably a relatively brief crisis is still uncertain. Newton had, after all, initiated this search for a public office in the early 1690s and in 1696 accepted the position of Warden of the Mint. 
Newton was well enough to continue correspondence with Pepys in November of the same year, patiently answering a number of letters about a mathematical problem related to dice. Pepys, clearly more interested in winning at the gaming table than understanding gaming theory, proved an inept pupil. Perhaps he felt Newton owed him something after the wild accusations but, equally, he may have seen this exchange of letters as an opportunity to reassure Newton that there was no need to “withdraw from your acquaintance”. If only the diary could have told us more.
To see Newton's Principia and learn more about Samuel Pepys's extraordinary life, visit Samuel Pepys: Plague, Fire, Revolution