‘You can almost hear the pen scratching over the surface’: Sir Isaac Newton’s revisions to his greatest work, the Principia

‘To be standing in front of something he wrote gives me goosebumps,’ says space scientist Dr. Maggie Aderin-Pocock, discussing with specialist Thomas Venning an unknown manuscript that has ‘slept in obscurity for 300 years’

In May 1694, the Scottish mathematician and astronomer David Gregory visited Isaac Newton in Cambridge.

Over the next six days, following discussions with the young scientist, Newton made extensive revisions to a work that had shaken the very foundations of science when it had first been published seven years earlier.

The work in question was the Philosophiae Naturalis Principia Mathematica, in which Newton attempted to explain the movement of everything in the universe, from a pea rolling on a plate to the planet Pluto. It was a remarkably ambitious and fiendishly complex task, and the results were startling.

Taking inspiration from Principles of Philosophy  by René Descartes, in which the French thinker set forth the laws of nature, Newton challenged himself to formulate three simple laws of motion that took in the concepts of inertia, acceleration, force, momentum and mass.


Enoch Seeman (1694-1744) and studio. Portrait of Sir Isaac Newton seated at a table with a copy of the Principia and an astrological globe

‘When the Principia  was published in 1687, it was groundbreaking,’ says Christie’s head of Books and Manuscripts Thomas Venning. ‘It changed the way we do science.’

On 8 July, Christie’s is selling a manuscript containing the revisions Newton made to the Principia  during those six days with Gregory.

‘Newton was planning to publish a second edition of the book,’ says the specialist. ‘He knew there were unanswered questions in the first edition that needed to be explored.’

‘The notes cover all three books of the Principia: essentially, you are getting the whole of Newton’s arguments in miniature’ — specialist Thomas Venning

This proposed revision was never completed, and it was not until 1713, under the editorship of Roger Cotes, that a second edition was eventually published.

‘Newton had great difficulty completing tasks,’ says Venning. ‘He needed a stimulus, which is what Gregory provided for a brief period in 1694.’

According to the specialist, Newton had suffered an intense nervous breakdown the previous year as a result of his work on the Principia.

‘We know from contemporary descriptions that he spent much of the time writing his laws of motion in almost total isolation. He hardly ate and rarely dressed. I think by the end he was exhausted, mentally and physically.’

As Venning explains, it is incredibly rare to find scientific papers by Newton on the market, because much of his archive is owned by Cambridge University: ‘It is still possible to acquire his writings on alchemy and theology, but not on science.’


Isaac Newton manuscript. Two pages of revisions to the Principia Mathematica. Estimate: £600,000-900,000. The Exceptional Sale, London, 8 July

The autograph manuscript is a fascinating insight into the workings of Newton’s mind. ‘The notes cover all three books of the Principia: essentially, you are getting the whole of Newton’s arguments in miniature.’

Like the Principia, the notes are written in Latin, because Newton wanted to reach an international audience of scholars and intellectuals.

Moreover, it is widely agreed that he set out to be deliberately obscure. Not wanting to be misinterpreted, he ensured that only a person capable of understanding astronomy, Latin and mathematics would be able to comprehend the Principia.

Nevertheless, Newton had plenty of detractors on first publication, principally from the followers of Descartes, who objected to his concepts of space and time.

Others found the idea that the workings of nature could be enshrined in a handful of laws incomprehensible. Newton was once greeted in Cambridge with the words: ‘There goes a man who has written a book neither he nor anyone else can understand.’


Isaac Newton manuscript. Two pages of revisions to the Principia Mathematica. Estimate: £600,000-900,000. The Exceptional Sale, London, 8 July

The astronomer Edmond Halley, who had paid for the publication, wrote in the introduction that it was ‘a divine book’, declaring that it was not safe to go nearer to God than Newton had done.

Indeed, Newton himself developed a godlike status in the years following publication.

‘What is interesting about this manuscript is that Newton hasn’t yet reached that stage of untouchability,’ says Venning. ‘He’s still open to Gregory’s critique and happy to be challenged.’

The manuscript remained with Gregory, who, thanks to Newton’s recommendation, had been appointed Savilian Professor of Astronomy at Oxford in 1691.

‘Most of Gregory’s papers were donated to the Royal Society in the 1860s, but some found their way onto the market,’ says the specialist. ‘The mid-19th century was a golden age of autograph collecting, and there would have been a huge appetite for something of this nature.’

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By the late 1790s, Newton had achieved astonishing prestige and the Principia  was considered revolutionary. The laws were refined over the years, but it took the modern genius of Albert Einstein to break the taboo and introduce new thinking to Newton’s theories.

‘Even so,’ says Venning, ‘it is Newton we can thank for putting a man on the moon and sending a rover to Mars.’

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