In which a Franciscan friar cuts away everything unnecessary—and accidentally sets the stage for the end of medieval philosophy
♦ ♦ ♦What do you know about Ockham's Razor? Nominalism? The simplification that followed Aquinas?
“Do not multiply entities beyond necessity.” This is Ockham's Razor, and it is the simplest, most powerful principle in philosophy. When two explanations explain the same thing equally well, choose the simpler one. Do not assume what you don't need to assume.
This principle, applied ruthlessly, will demolish Aquinas' cathedral.
William of Ockham was born around 1287 in a small village in Surrey, England. He was a Franciscan friar, and as a Franciscan, he belonged to an order that valued poverty and simplicity. This is key to understanding his philosophy: he was not trying to be clever or iconoclastic. He was trying to be simple.
By Ockham's time, medieval philosophy had become enormously complex. Aquinas' synthesis was magnificent but intricate. He posited universals (the form of “humanity” that all humans share), essences distinct from existence, multiple layers of being. Each layer required explanation. The system was complete and elaborate.
Ockham asked: do we really need all of this? Can we explain what we observe using fewer assumptions?
Ockham's radical answer was nominalism: universals do not exist. There is no general form of “humanity.” There are only individual humans. The word “humanity” is a name (nomen in Latin—hence “nominalism”) we apply to the collection of individual humans. But the universal itself has no real existence.
This seems like a small point, but it was revolutionary. If universals don't exist, then the entire Platonic and Aristotelian framework that Aquinas built on collapses. Plato's Forms? Gone. Aristotle's essences? Gone. Ockham replaced them with a simpler picture: the world consists of individual things and our names for groups of individual things.
Ockham's razor cut in three directions simultaneously:
Do not assume that universals exist. Explain everything through individual things and our concepts.
Do not multiply entities (beings, essences, qualities) beyond what observation requires. A simpler ontology is preferable.
Do not accept a doctrine just because Aristotle or Aquinas said it. Use your own reason to examine what can be known from experience.
Ockham also challenged the authority of the Church in temporal matters. He argued that the Church and state have distinct spheres. This was radical in his time. His political writings on the separation of church and state were as revolutionary as his metaphysics.
Because of his views, Ockham was summoned to Avignon in 1324 to answer charges of heresy. He was never formally condemned, but he spent the rest of his life in exile, at the court of King Louis of Bavaria. He died in 1347, probably from the plague.
Ockham's influence extends far beyond medieval philosophy. His three key ideas shaped everything that followed.
The simplest explanation that accounts for the facts is preferable to a complex one.
This principle has become foundational in science. When Newton and Einstein developed their theories, they applied Ockham's razor—simpler equations explained more. Modern physics is Ockhamic: find the simplest laws that account for observation.
But notice: this is not the same as truth being simple. Reality might be complex. But we should prefer simpler explanations unless we have evidence for complexity.
Only particular things exist. Universals are names, not entities.
This leads directly to empiricism. If only individuals exist, then knowledge must come from experience of individuals. General principles and universal laws must be derived from observation of particulars. This is the foundation of the scientific method.
A claim is not true just because an authority says it. Use reason to examine it.
This is the most dangerous idea, from the perspective of the medieval establishment. Ockham is not saying reason is infallible. He is saying reason is necessary. You cannot hide behind Aquinas or Aristotle. You must think for yourself.
Ockham intended to defend faith by clearing away unnecessary metaphysical complications. But his razor cut so deeply that it undermined the entire framework that medieval theology depended on. When you remove universals, you remove the basis for natural theology. When you remove essences, you remove the foundation for virtue ethics. When you assert the autonomy of reason from authority, you open the door to challenges to authority itself.
Medieval philosophy was built on the synthesis of faith and reason, particularly through universals and essences. Ockham's nominalism and empiricism made that synthesis impossible. Philosophy had to find a new path.
Three dates to lock into memory using your PAO system.
The Franciscan friar who would wield the razor is born in England. Encode “12” and “87” from your PAO. Link to a baby born holding a razor, ready to cut away excess.
Ockham's ideas are deemed dangerous to orthodoxy. Encode “13” and “24” from your PAO. Link to a friar called before a tribunal, his razor confiscated, his ideas challenged.
Medieval philosophy ends with his death (and the beginning of the plague). Encode “13” and “47” from your PAO. Link to the razor falling from his hand, its work done.
Cover the dates above. Can you recall all three?
1. When was Ockham born?
2. When was he summoned to Avignon?
3. When did he die?
You have now reached the thirtieth location, the exact midpoint of your 50-lesson journey. This is where medieval philosophy ends and the modern world begins. Ockham wields his razor and cuts away the entire Aquinas synthesis. After this, philosophy will never be the same.
Your 30th location holds The Razor—Ockham and the end of the medieval synthesis. Place five vivid images here.
1. A razor, impossibly sharp, catching light—Ockham's principle made visible. Do not multiply entities beyond necessity.
2. Aquinas' cathedral, perfect and complete, beginning to crumble—stones falling as the universals and essences that held it together dissolve. The grand synthesis breaks apart.
3. Plato's realm of Forms, fading like a ghost—Universals are only names, not things. The eternal Forms that inspired philosophy for 2,000 years vanish into concepts.
4. A single individual thing, standing alone, sharply defined and real—a person, an object. This is all that exists. Everything else is our naming of it.
5. A friar in exile, holding the razor, looking back at the ruined cathedral—William of Ockham did not intend to destroy medieval philosophy. But the razor he wielded cut too deep.
Describe exactly where you place each image. You are halfway through your palace now.
Choose 2–3 of these questions to reflect on.
Is the simplest explanation actually the truest? Or might reality be genuinely complex? How do we know when we're oversimplifying?
Ockham says universals are just names. But what about the concept of “humanity” that all humans share? Is that just a name, or something real?
Ockham meant to defend faith. Instead, his razor destroyed the framework medieval theology depended on. Is it dangerous to simplify too much?
Ockham says: don't accept something just because an authority says it; think for yourself. Is this what we need, or does it lead to chaos?
Ockham argued church and state should be separate. This was radical in his time. Is this a good separation, or does one side need authority over the other?
You are halfway through this course. Medieval philosophy ends here. What has changed from Lesson 1 to Lesson 30? What endures?
Ockham died during the Black Plague, which killed a third of Europe. How does catastrophe reshape philosophy? What happens when the world breaks?
Start the timer, then write everything you can remember from this lesson without looking back.
Don't look back. Retrieve from memory.
c. 1287 AD—Birth of William of Ockham
1324 AD—Summoned to Avignon for heresy trial
1347 AD—Death of William of Ockham
Name and describe them:
Ockham's Razor: Do not multiply entities beyond necessity. The simplest explanation is preferable.
Nominalism: Universals are not things; they are names. Only individuals exist.
Authority of Reason: Do not accept a claim just because an authority says it. Use reason.
What was the consequence of Ockham's nominalism for medieval philosophy?
By denying universals and essences, Ockham undermined the entire framework of medieval theology. The Platonic-Aristotelian synthesis that Aquinas built on collapsed. Natural theology based on essences and universals became impossible. Medieval philosophy was over.
Walk through Location 30. List the 5 images:
You have completed 30 lessons and reached the midpoint of the course. Medieval philosophy has ended. What do you think comes next? What new questions will arise in the modern world?
From Thales to Ockham: 2,400 years of philosophy, compressed into 30 lessons. You have climbed from the Milesians through Plato and Aristotle, through Augustine and Aquinas, to the razor of Ockham. The ancient and medieval worlds are behind you. You have placed 30 vivid images in your palace. You have encoded 90 dates using your PAO system.
The next twenty lessons will move through Renaissance humanism, the Reformation and counter-Reformation, the Scientific Revolution, the Enlightenment, and into modernity. The question “How should we live?” will become more urgent. And the deepest question—how to heal the wound of guilt and shame that no reason alone can touch—will draw into view.
This lesson's content returns in: Lesson 33 (+3), Lesson 37 (+7), and Lesson 44 (+14).