William of Occam: the patron saint of the modern secular world

The simplifying principle of Occam’s Razor served to sever science from religion

On the night of May 26th, 1328, three Franciscan friars slip out of the papal city of Avignon and ride south to the Crusader port of Aigues-Mortes. Two were senior members of the order whereas the third was a little-known English scholar, William of Occam. If captured, they could face excommunication, imprisonment or even a slow death on a burning pyre.

We know little of William’s early years, only that he was born in the Surrey village of Occam and given to the Franciscan order as a child. The Franciscans sent him to the University of Oxford to study the science of theology. That there was such a discipline seems very odd today, but throughout most of human history, there hadn’t really been a distinction between the natural and supernatural.

More than a thousand years earlier, Aristotle attempted to pull a thread of science out of observations such as “everything that moves is moved by another” But he also drifted into his metaphysics by arguing that, to avoid an infinite regress of movers, there had to be a first cause or prime mover. He also believed that some causes lay in the future, in the form of the purpose of objects or actions. So, the purpose of trees was to provide wood, the purpose of wood was to provide fire, the purpose of fire was to warm humans. He again capped this otherwise infinite regress with the prime mover.

Aristotle was also keen on categorising and provided the first stab at biological taxonomy by dividing plants and animals into categories. However, he based his categorisation on the notion of invisible but real universals, which are kind of invisible essences of objects. So cats became cats because they were filled with a feline universal, dogs with a canine universal and so on. He extended the universal idea into every category of being, so universals of redness, roundness, chairness, fatherness and so on was what made objects red, round, fathers or chairs.


Aristotle’s prime mover was more of an it than a him, but was nevertheless enthusiastically incorporated into Christianity by the greatest theologian of the Middle Ages, Thomas Aquinas. Aquinas imported Aristotle’s framework to construct a kind of scientific theology whose closest parallel today might be the “experimental theology” in Philip Pullman’s His Dark Materials novels. Its cornerstone was five proofs of God constructed with Aristotle’s chains of reasoning but the Christian God replacing both the prime mover and final cause. Aquinas also imported Aristotle’s universals as ideas in God’s mind so their study became a route to the divine, so theology became a science. By a clever manipulation of the universal idea, Aquinas even claimed to have incorporated the Eucharist miracle into his theological science.

Aquinas’s theology came to dominate Christianity. If its fusion with science had survived then science in the West might have suffered the same stagnation under the weight of dogma that it suffered in so many other parts of the world. Fortunately, William of Occam had a tool sharp enough to sever the link.

William of Occam is most famous for insisting that “entities should not be multiplied beyond necessity”. Occam’s razor advises that we should only accept the simplest solution to a problem, as long as it works. He used his razor to argue first that universals are entities beyond necessity because “fathers are fathers [simply] because they have sons”, dogs because they bark etc. With universals dismissed, scientific theology and its route to God tumbled. It collapsed completely after Occam went on to demolish all five of Aquinas’s so-called proofs of God. For example, he argued that final causes or purposes are also entities beyond necessity writing that “why does the fire heat the wood … it is its nature”.

Occam maintained that the only route to God is through faith, not reason, whereas reason, rather than faith, is the path to science. To assure the independence of science, he advised that “assertions, especially in physics, which do not pertain to theology should not be officially condemned or prohibited by anyone because in such things everyone should be free so that they may freely say what they please”.

As far I am aware, William is the first person in the history of the world to so clearly separate science from religion. Nearly all the greatest scientists up to the 20th century embraced Occam’s separation and his razor.

Back in the 14th century, William’s radical ideas caused consternation within the cloisters of Oxford. A former chancellor argued that his elimination of universals threatened the Catholic faith by knocking holes in Aquinas’s interpretation of the Eucharist miracle. About two centuries later, this same issue would precipitate the Reformation. Early in 1324, it precipitated a summons that arrived in Oxford, charging William to attend trial at the papal seat in Avignon to face charges of teaching heresy.

William reached Avignon probably early in the summer of 1324. His trial was lengthy and, in 1327, Pope John XXII issued a bull charging Occam with having uttered “many erroneous and heretical opinions”. However, by this time William had become embroiled in an even more dangerous conflict between the Pope and the Franciscan order.

Founded by St Francis, the Franciscans insisted that the surest way to holiness was to follow Jesus’s example of abandoning wealth to live in a state of apostolic poverty. The wealthiest man in Christendom, Pope John XXII, who was busy building the magnificent Palais de Papes in Avignon, disagreed. The dispute was pinned onto the seemingly trivial issue of whether Jesus owned a purse. The Franciscans were scandalised whereas Pope John insisted that Jesus not only owned a purse but, as the son of God, one filled with ownership of the world.

This was a pivotal notion in the Middle Ages because the papacy claimed that, on his death, Jesus had bequeathed ownership, or dominion – considered to be another universal – to St Peter who bequeathed it to succeeding popes, who bestowed it on Christian kings, who divided it out amongst their nobles. Nearly 200 years later and Pope Alexander VI claimed this same divine dominion to divide South America between the Spanish and Portuguese crowns.

Despite the heresy charges, as the cleverest scholar at their disposal, the Franciscans gave William the job of deliberating on John XXII’s arguments. Occam concluded that not only was the Pope wrong, but his writings proved him to be a heretic. This is what provoked the Franciscans’ flight, chased by a posse of Vatican soldiers. They escaped to board a ship which took them to Italy and the protection of the Holy Roman Emperor, who happened to be crowning a rival Pope in Rome at the time.

William spent the rest of his life under the protection of the Holy Roman Emperor. He continued to attack papal authority and was pursued by agents of several popes, one of whom threatened to burn down the town of Tournai in modern-day Belgium to capture the fugitive.

On the vexed question of apostolic poverty vs papal dominion, William upended the entire medieval world order by insisting that God has given everyone the same natural right to sustenance, safety and shelter. These rights were real, but money, property and dominion were entirely human inventions that, like the universal of fatherhood, only existed in the minds of people who believed in them. So, the Pope’s claim for worldly dominion was as empty as Jesus’s purse.

William also insisted that the authority of rulers derived from the ruled “from God through his people” and that “power should not be entrusted to anyone without the consent of all”. Since pagans and infidels were also descended from Adam and Eve, they had inherited the same natural rights as Christians.

William of Occam was excommunicated after fleeing Avignon, but this was rescinded by Pope Innocent VI in 1359. His razor, insisting on the simplest solutions, remains central to science and is an invaluable adversary against pseudoscience, dogma, conspiracy theories or general baloney.

As a fearless defender of natural rights against institutional authority and the first to clearly separate science from religion, he is a worthy contender for the title of patron saint of our secular world.
Life is Simple: How Occam's Razor Set Science Free And Unlocked The Universe by Johnjoe McFadden is published by Basic Books. John Banville will review it in The Irish Times later this month