a young scholar, More had shared many of Descartes’s ideas and had initially seen Cartesian philosophy as a means of reconciling theology and natural philosophy; but gradually he had turned away from this view, later becoming its vehement opponent. At the root of More’s ideology, and of his influence on Newton, was an amalgamation of atomism and Christian Platonism. Plato had believed in the notion of spirit, an essence within all things, manifest in man as the soul, but also an extension of God, a force at work in Nature, guiding the universe. In Descartes’s philosophy there appeared to be no continuing need for God. Descartes never intended this interpretation and was himself a devout Christian, but to More, and later to Newton, the mechanisms and ideas portrayed in Descartes’s Discourse on the Method and Principles of Philosophy could easily be interpreted as atheistic. In More’s universe, matter was guided by spirit, manipulated by God entirely at his discretion.
More, who was born in Grantham, had tutored Joseph Clark (the brother of Clark the apothecary) at Cambridge. He visited Grantham occasionally, and it is possible that he may thus have met Newton several years before the young man entered university. It is clear from entries in his philosophical notebook that Newton came under More’s influence quite early in his university career. As well as the mention of a text by ‘the excellent Dr More’ in his notes on atomism, Newton has listed headings clearly influenced by More’s main areas of interest, such as ‘Of the Creation’, ‘Of the Soule’ and ‘Of God’.19 These may have been prompted by Newton’s natural curiosity for things spiritual, but it is also likely that they stemmed from reading More’s most important book, The Immortality of the Soul, to which Newton had referred in the earlier entry ‘Of Atoms’.
More’s influence upon Newton extended beyond the inspiration provided by his writings.20 Newton’s ideas and loyalties changed so radically within such a short period of time during his second year at university that the influence of at least one academic guide is likely. Having been Clark’s tutor and an associate of Babington, More probably talked to Newton on a number of occasions during the young man’s final years in Grantham and Woolsthorpe and may even have singled him out upon his entry into the university. He was another father-figure within the academic and social network forming around the serious-minded and inquisitive young man. Although Babington was more of a practical guide (and almost certainly provided access to his private library), he was in Cambridge only rarely. More provided a greater and more lasting intellectual foundation.
But, if More’s influence was strong, to the modern mind he seems to have offered a confusing philosophy. To us, atomism is the foundation of modern physics, but the seminal work of Rutherford, who first postulated the existence of smaller particles within the atom, early in the twentieth century, led to the oddities of quantum theory. From this derives indeterminism, as expressed in Heisenberg’s Uncertainty Principle, leading to theories of unpredictability and a philosophical viewpoint far removed from the image of a universe manipulated by a benign God. Though some have managed to visualise and have faith in a strange marriage between quantum theory and God, mainstream modern atomism could not be further removed from More’s idea of a personal, all-pervading deity. Yet, to More – naturally unaware of where it would one day lead – atomism was a way of proving the actions of an omnipresent Creator, a confirmation of the Testaments; because, as Newton had underscored in his notebook, matter could be divided only to a finite degree, and the resulting fundamental particles must have been created and guided by a divine hand.
If More offered a theoretical foundation which combined natural philosophy with theology, from reading Galileo and Bacon contemporaneously Newton had also learned how to construct a working system with which to verify his ideas. By the summer of 1664 he was able to state in his notebook that ‘The nature of things is more securely and naturally deduced from their operations one upon another than upon the senses. And when by the former experiments we have found the nature of bodies … we may more clearly find the nature of the senses.’21 What he means by this is that scientists cannot simply trust what they observe with their senses, but need to experiment before attempting to deduce the nature of the universe and the objects that fill it – that there may be more going on than we know from the information our senses give us by superficial observation.
Newton’s first experiments, begun during the summer of 1664, were probably his investigations into the nature of light. Years later these appeared in the Opticks, first published in 1704.
His earliest interest in light began when he bought a glass prism at the Stourbridge fair, held on a piece of land beside the river about a mile from the centre of Cambridge. Amid stages for the jugglers and clowns, minstrels and children’s games, dancers and actors stood stalls selling all manner of oddities – trinkets from exotic travels in Bohemia, potions and elixirs, and toys. It was from such a stall that Newton purchased his prism.
According to Conduitt, ‘In August 1665, Sir I. bought a prism at Stourbridge fair to try some experiments upon Descartes’s books of colours.’22 However, on this occasion Conduitt got his dates wrong and Newton actually acquired the prism on his visit to the fair in 1664, not 1665. Plague prevented the holding of the fair in 1665 – a fact documented in the diary of Alderman (later Mayor) Samuel Newton (no relation): ‘On the first of September, a proclamation was posted prohibiting Stourbridge fair on account of the great plague in London.’23 It is also agreed by most authorities that, because of the plague, Newton had left Cambridge to return to Woolsthorpe before the beginning of August 1665, and was absent from the university for most of the next two years.24
The prevailing hypothesis of light at the time was that of Descartes. He believed that light was a ‘pressure’ transmitted through the transparent medium of the ether. Sight, he claimed, was due to this pressure impinging upon the optic nerve.
Newton was acquainted with this hypothesis and had already made notes on the subject in his philosophical notebook. But it is likely that, in keeping with his support for atomism, by the summer of 1664 he was beginning to doubt the accuracy of Descartes’s explanation. He was already thinking that light might be corpuscular, and by imagining light to be particle-like he was more readily able to explain phenomena such as reflection, refraction, and optical and chromatic distortions. Writing to Henry Oldenburg, the Secretary of the Royal Society, some eight years later, Newton described his earliest experiments with the prism:
I procured me a triangular glass-prism, to try therewith the celebrated Phenomena of Colours. And in order thereto having darkened my chamber, and made a small hole in my window-shuts, to let in a convenient quantity of the sun’s light, I placed my prism at its entrance, that it might be thereby refracted to the opposite wall. It was at first a very pleasing divertissement, to view the vivid and intense colours produced thereby …25
With the prism he was able to demonstrate how white light is composed of a range of component colours and how it can be split into the colours of the spectrum, with blue light, at one end of the spectrum, being bent (or refracted) more markedly than red light, at the other end. Furthermore, he was able to judge – correctly – that the colour of an object depends upon which part of the spectrum is absorbed by it and which part reflected. ‘Hence redness, yellowness etc.,’ he wrote, ‘are made in bodies by stopping the slowly moved rays without much hindering of the motion of the swifter rays, & blue, green & purple by diminishing the motion of the swifter rays & not of the slower.’26
In short, an object will look red if the other colours (what Newton refers to as ‘the slowly moved
