Most people associate Isaac Newton with gravity. Of all the forces of nature, gravity is the one whose effects are most obvious to us, and have been since prehistoric times. Everyone knows that an apple falls vertically downwards, as if drawn towards the centre of the Earth. Anyone who has spent any time gazing up at the night sky knows that the Moon and planets follow regular, predictable orbits. But obvious as these things are, the ultimate explanation – that they are all due to the same universal force – is far from obvious.

Newton did more than just wave his hands in the air and say ‘look, there’s a universal force of attraction between all material things’. He came up with a precise mathematical equation to describe that force. In the course of time, this equation would allow his successors to discover new planets, to predict the reappearance of comets and to travel to the Moon.

Newton made the single greatest breakthrough in the history of physical science…but it wasn’t his discovery of the law of gravity. It was an even more fundamental discovery: that it is possible to predict the behaviour of the physical world by representing it in the form of mathematical symbols and equations. The implications of this discovery reach beyond theoretical physics into all branches of engineering and technology. It is no exaggeration to say that the modern, high-tech world we live in today wouldn’t exist without it.

For Newton, mathematics was the key that unlocked the secrets of the universe. To most of his contemporaries, Aristotle’s two-thousand-year-old system of ‘natural philosophy’ still provided the standard picture of the physical world – and Aristotle’s theory contains no mathematics. But when Newton published his masterpiece in 1687, he called it Philosophiae Naturalis Principia Mathematica – Mathematical Principles of Natural Philosophy. The book was a revolution, and the essence of that revolution is summed up in the title. Before 1687, Mathematical Principles and Natural Philosophy were two completely different branches of knowledge, poles apart. After Principia they would be tied together by a bond that has become more and more powerful in the intervening centuries.

Newton’s genius lay in the fact that he looked for a mathematical key to the universe and found it. The basic idea, however, was not a new one. Some of the pre-Aristotelian Greek philosophers – notably Pythagoras and his followers – did believe in a fundamentally mathematical world, but over time their views had fallen out of favour. More often than not such ideas were dismissed as the musings of crackpots or mystical dreamers. A similar attitude prevailed towards the Hermetic philosophers of mediaeval Europe – a small and secretive minority who believed that, with sufficient diligence, it would be possible to discover a simple set of rules capable of explaining the complexities of the natural world.

The situation in Newton’s time was, in a sense, the mirror image of the present day. What then seemed to be a bizarre and mystical notion – that the universe obeys simple mathematical laws – is now seen as the 'rational' view. But in those days, 'rational' people tended to assume the exact opposite. The world looks complex, chaotic and unpredictable…so clearly it can have nothing to do with the elegance and simplicity of mathematics.

Just as most people today know that Newton discovered the law of gravity, there is also an increasing awareness that he dabbled in topics like alchemy, Hermeticism and theology. ‘Dabbled’ is an understatement, though: he spent far more time on these subjects than on the scientific work he is remembered for. His world-view was driven by the fundamental belief that God created an ordered universe, and he devoted his life to developing a better understanding of that creation by every means available to him.

Today we might divide up Newton’s work into ‘scientific’ and ‘non-scientific’ pigeonholes, but for him they were all part and parcel of the same basic quest. As the economist and Newton scholar John Maynard Keynes wrote: ‘He looked on the whole universe and all that is in it as a riddle, as a secret which could be read by applying pure thought to certain evidence, certain mystic clues which God had laid about the world.’

It is difficult to avoid the conclusion that Newton’s greatest scientific and mathematical achievement – the foundation stone of modern rational science – was the fruit of a broader project which today would be dismissed as mystical nonsense. To Newton, mathematics was nothing less than the language of God. As confirmation of this, he cited chapter 11, verse 20 of The Wisdom of Solomon: ‘Thou hast ordered all things in measure and number and weight.’ Just like the Christian fundamentalists whom modern scientists consider to be their arch opponents, Newton looked to the Bible as the ultimate authority.

Taken in isolation from his accomplishments, it would be easy to dismiss Newton’s world-view on the grounds that countless astrologers, alchemists, Hermeticists and New Agers have held similar views before and since. But Newton was unique. He succeeded where so many others have failed. He discovered a key to the universe – applied mathematics – which actually works.

By Andrew May