The Clockwork Universe: Isaac Newton, the Royal Society, and the Birth of the Modern World - Edward Dolnick (2011)

Part III. Into the Light

Chapter 39. All Mystery Banished

Isaac Newton believed that he had been tapped by God to decipher the workings of the universe. Gottfried Leibniz thought that Newton had set his sights too low. Leibniz shared Newton’s yearning to find nature’s mathematical structure, which in their era meant almost inevitably that both men would mount an assault on calculus, but in Leibniz’s view mathematics was only one piece in a much larger puzzle.

Leibniz was perhaps the last man who thought it was possible to know everything. The universe was perfectly rational, he believed, and its every feature had a purpose. With enough attention you could explain it all, just as you could deduce the function of every spoke and spring in a carriage.

For Leibniz, one of the greatest philosophers of the age, this was more than a demonstration of almost pathological optimism (though it was that, too). More important, Leibniz’s faith was a matter of philosophical conviction. The universe had to make perfect sense because it had been created by an infinitely wise, infinitely rational God. To a powerful enough intellect, every true observation about the world would be self-evident, just as every true statement in geometry would immediately be obvious. In all such cases, the conclusion was built in from the start, as in the statement “all bachelors are unmarried.” We humans might not be clever enough to see through the undergrowth that obscures the world, but to God every truth shines bright and clear.

In fact, though, Leibniz felt certain that God had designed the world so that we can understand it. Newton took a more cautious stand. Humans could read the mind of God, he believed, but perhaps not all of it. “I don’t know what I may seem to the world,” Newton famously declared in his old age, though he knew perfectly well, “but, as to myself, I seem to have been only like a boy playing on the seashore, and diverting myself in now and then finding a smoother pebble or a prettier shell than ordinary, whilst the great ocean of truth lay all undiscovered before me.”

Newton’s point was not simply that some questions had yet to be answered. Some questions might not have answers, or at least not answers we can grasp. Why had God chosen to create something rather than nothing? Why had He made the sun just the size it is? Newton believed that such mysteries might lie beyond human comprehension. Certainly they were outside the range of scientific inquiry. “As a blind man has no idea of colors,” Newton wrote, “so have we no idea of the manner by which the all-wise God perceives and understands all things.”

Leibniz accepted no such bounds. God, he famously declared, had created the best of all possible worlds. This was not an assumption, in Leibniz’s view, but a deduction. God was by definition all-powerful and all-knowing, so it followed at once that the world could not have been better designed. (Even for one of the ablest of all philosophers, this made for an impossible tangle. If logic compelled God to create the very world we find ourselves in, didn’t that mean that He had no choice in the matter? But surely to be God meant to have infinite choice?)

Voltaire would later take endless delight, in Candide, in pummeling Leibniz. On Candide’s very first page, we meet Leibniz’s stand-in, Dr. Pangloss, the greatest philosopher in the world. Pangloss’s specialty is “metaphysico-theologo-cosmolonigology.” The world, Pangloss explains contentedly, has been made expressly for our benefit. “The nose is formed for spectacles, therefore we wear spectacles. . . . Pigs were made to be eaten, therefore we eat pork all the year round.”

Pangloss and the hero of the novel, a naïve young man named Candide, spend the book beset by calamity—Voltaire cheerily throws in an earthquake, a bout of syphilis, a stint as a galley slave, for starters. Bloodied and battered though both men may be, Pangloss pops up from every crisis as undaunted as a jack-in-the-box, pointing out once more that this is the best of all possible worlds.

This was great fun—Voltaire was an immensely popular writer, and Candide was his most popular work—but it was a bit misleading. Leibniz knew perfectly well that the world abounded in horrors. (He had been born during the Thirty Years’ War.) His point was not that all was sunshine, but that no better alternative was possible. God had considered every conceivable universe before settling on this one. Other universes might have been good, but ours is better. God could, for instance, have made humans only as intelligent as dogs. That might have made for a happier world, but happiness is not the only virtue. In a world of poodles and Great Danes, who would paint pictures and write symphonies?

Or God might have built us so that we always chose to do good rather than evil. In such a world, we would all be kind, but we would all be automatons. In His wisdom, God had decided against it. A world with sin was better than a world without choice. Not perfect, in other words, but better than any possible alternative. It was this complacency that infuriated Voltaire. He raged against Leibniz not because Leibniz was blind to the world’s miseries but because he so easily reconciled himself to them.

But Leibniz’s God was as rational as he was. For every conceivable world, He totted up the pros and cons and then subtracted the one from the other to compute a final grade. (It is perhaps no surprise that Leibniz invented calculus; in searching for the world that would receive the highest possible score, God was essentially solving a calculus problem.) Since God had necessarily created the best of all possible worlds, Leibniz went on, we can deduce its properties by pure thought. The best possible world was the one that placed the highest value on the pursuit of intellectual pleasure—here the philosopher showed his hand—and the greatest of all intellectual pleasures was finding order in apparent disorder. It was certain, therefore, that God meant for us to solve all the world’s riddles. Leibniz was “perhaps the most resolute champion of rationalism who ever appeared in the history of philosophy,” in the words of the philosopher Ernst Cassirer. “For Leibniz there . . . is nothing in heaven or on earth, no mystery in religion, no secret in nature, which can defy the power and effort of reason.”

Surely, then, Leibniz could solve the problem of describing the natural world in the language of mathematics.