Welcome to the next stage of our historical survey. In the last lesson, we explored the intensely practical philosophies of the Hellenistic period, where Stoicism and Epicureanism provided comprehensive blueprints for living. We concluded by noting that we would now leap forward to the intellectual world of medieval Europe, where the philosophical inheritance of Greece was integrated into a profoundly different, Christian theological framework.
This lesson addresses a central preoccupation of medieval thought: the problem of universals. We have already touched on this in comparing Plato's and Aristotle's views, but the medievals sharpened the debate into a foundational conflict that shaped metaphysics, logic, and theology for centuries. Our goal is to understand the core positions in this debate, primarily those of realism and nominalism, and to appreciate what was at stake.
1. What's the Problem? Universality and Knowledge
Before we dive into the medieval arguments, it's worth taking a moment to see why this problem is so fundamental. Given your background in mathematics and physics, consider the proof of a simple geometric theorem, like Thales's theorem, which states that any triangle inscribed in a semicircle is a right triangle.
The Medieval Problem of Universals
The Stanford Encyclopedia of Philosophy (SEP) article on this topic opens with a superb example that illustrates precisely what is at stake in the problem of universals.
Please read the introductory paragraphs and the section titled The Emergence of the Problem. The key insight here is that a geometric proof is not about the specific, imperfect triangle drawn on a page, but about some ideal or universal triangle. The question is: what is the nature of this universal triangle? Does it exist?
As the article points out, the demonstration seems to be about a perfect, universal "triangle" that we grasp with our intellect, not any particular one we see with our eyes. Yet, the idea of a universal triangle that is somehow neither scalene nor isosceles, yet must be one or the other, seems logically impossible. This paradox is the heart of the problem. How can we have universal knowledge, which is the bedrock of science and mathematics, if all we ever encounter are particular things, and the very idea of a "universal thing" seems contradictory? This is the challenge the medieval thinkers inherited.
2. Setting the Stage: Boethius's Formulation
The medieval debate was formally launched by the Roman philosopher Boethius (c. 480–524), who translated Aristotle's logical works into Latin. While translating an introduction to Aristotle by the Neoplatonist philosopher Porphyry, Boethius encountered and articulated a set of questions that would frame the discussion for the next thousand years.
A History of Philosophy | 23 Problem of Universals
This lecture clip, from a course by the late Dr. Arthur Holmes, provides a concise overview of the questions Boethius posed.
Watch from the opening section where the lecturer lays out Boethius's three questions and a fourth that was added to the discussion. These questions structure the entire debate.
To summarize, the key questions are:
- Do universals (genera and species) exist in reality, or are they mere mental constructs?
- If they exist in reality, are they material or immaterial?
- If they exist, are they separate from particular things or do they exist within them?
- Do we think of universal concepts separately from particulars?
These questions give rise to a spectrum of positions. At the two extremes are Realism, the view that universals have some form of existence outside the mind, and Nominalism, the view that only particulars exist and universals are merely names or words (nomina).
Medieval thinkers often used a tripartite classification for the possible locations of universals:
- Universalia ante rem: Universals before the thing. This corresponds to the Platonic idea of Forms or, in a Christian context, ideas in the mind of God.
- Universalia in re: Universals in the thing. This corresponds to the Aristotelian idea of forms that are instantiated in and inseparable from particular objects.
- Universalia post rem: Universals after the thing. This refers to concepts that the mind abstracts from experience of particulars.
The debate, then, is about which of these (if any) are the primary locus of universality and what their ontological status is.
3. The Realist Camp: From Exaggeration to Moderation
Realists hold that terms like 'humanity' or 'triangularity' correspond to something real outside the mind. However, they differed significantly on the nature of this reality.
3.1 Exaggerated Realism
The most extreme form of realism, drawing from a strong Platonic influence, holds that a universal is a single entity, numerically one, in which all its particulars "participate." For example, 'humanity' is one real thing, and Socrates, Plato, and you are all human by participating in this single entity.
This view, however, was famously and decisively refuted by the brilliant 12th-century philosopher Peter Abelard.
The Problem of Universals - Medieval Philosophy (History of Philosophy)
This video, "The Problem of Universals" from Philosophy Overdose, gives a wonderfully clear account of a key moment in the debate: Abelard's critique of his teacher, William of Champeaux, who defended an exaggerated realist position.
Please watch the section describing Abelard's refutation of William's realism. Pay close attention to Abelard's two main objections: If humanity is one and the same substance in both Socrates and Plato, then Socrates and Plato are the same substance, differing only in their accidental properties. This one substance (humanity) would have to possess contradictory properties simultaneously (e.g., being in Athens and being in Rome, being seated and standing).
Abelard’s critique showed that this naive version of realism leads to logical absurdity. For a universal to be a single thing in the same way a particular is a thing is untenable.
3.2 Moderate Realism: Abstraction and Common Natures
A much more sophisticated and enduring form of realism was developed from Aristotelian foundations, championed by figures like Thomas Aquinas. This view denies that universals are separate "things" but insists they have a real foundation in particulars.
The key mechanism is abstraction. Boethius first laid the groundwork for this solution.
The Medieval Problem of Universals
Let's return to the SEP article to see how Boethius resolves the paradoxes of a really existing universal.
Please read the section Boethius’ Aristotelian Solution. The crucial move is distinguishing the mode of being of a thing from the mode of representation in the mind. The mind can consider in isolation (abstract) features that cannot exist in isolation. For example, you can think of "triangularity" without thinking of it as either isosceles or scalene, even though any existing triangle must be one or the other.
Building on this, later realists like Aquinas, influenced by the Arab philosopher Avicenna, developed the doctrine of the common nature. This view makes a three-fold distinction:
- The nature as it exists in particulars: Here, the nature (e.g., humanity) is individualized and multiplied. The humanity of Socrates is numerically distinct from the humanity of Plato.
- The nature as it exists in the mind: Here, the nature exists as a universal concept, abstracted from all individuating conditions. It has the property of universality.
- The nature considered absolutely: This is the nature in itself, abstracting from its existence in both particulars and the mind. In this absolute consideration, the nature is neither one nor many, neither particular nor universal.
This absolutely considered nature is what is predicated of individuals. It is the same nature in Socrates and in the mind, but its mode of being is different in each case. Think of the information content of a book. It is the same "book" that exists as a physical object on your shelf and as a digital file on your e-reader, but its instantiation is different. Likewise, "humanity" is the formal content that is realized in both the individual person and the universal concept.
4. The Anti-Realist Camp: Conceptualism and Nominalism
On the other side of the spectrum are those who deny that universals have any reality outside the mind.
4.1 Conceptualism: Abelard's Middle Way
As we saw, Abelard devastated extreme realism. But he didn't simply say universals are nothing. His own position, often called conceptualism (or sometimes moderate nominalism), offers a nuanced alternative. He agreed with the nominalists that no universal thing exists in reality. However, he disagreed with more radical nominalists who claimed we don't even have universal concepts. For Abelard, universality is a feature of our concepts, which we form by abstraction.
The word "human" is universal because it is applied based on a common concept, which in turn is grounded in a common status of things—the status of "being a man." This status is not a thing, but it is the real, common reason why the universal term is applied to all men.
4.2 Radical Nominalism: William of Ockham
The most famous nominalist, William of Ockham (c. 1287–1347), took a more radical approach, famously expressed in his principle of parsimony, or "Ockham's Razor": Entia non sunt multiplicanda praeter necessitatem ("Entities should not be multiplied beyond necessity").
Ockham applied this razor to the metaphysical clutter of the realists. He argued that there is no need to posit mysterious "common natures" or "statuses" to explain universality. All that exists in the mind-independent world are individuals.
For Ockham, a universal is simply a concept in the mind (which is itself a particular mental act) that has a specific function: it can signify or stand for multiple individuals. A concept is universal not because it corresponds to a universal object, but because of its universally representative function. For example, your concept 'cat' is not a universal cat-thing; it's a particular mental sign that you use to think about any and all particular cats indifferently.
This represents a major shift. For Ockham, universality is not an ontological feature of the world but a semantic one. It's about how our signs (mental and linguistic) refer to things.
5. The Two Ways: Via Antiqua vs. Via Moderna
Ockham's nominalism was so influential that it marked a major turning point in medieval philosophy, ushering in the via moderna ("the modern way") in contrast to the realist via antiqua ("the ancient way").
The fundamental difference can be visualized by comparing their conceptual schemes. The realists (via antiqua) proposed a complex hierarchy of items to bridge the gap between a word and the things it refers to.
This diagram from the SEP article illustrates the complex framework of the realist 'via antiqua'. Notice the many intermediaries between the common term and the singular things: subjective and objective concepts, intelligible species, and absolute natures.
In this realist view, a term like 'man' signifies an objective concept, which expresses an absolute nature, which is instantiated in individual natures within singular things.
Ockham and the nominalists (via moderna) swept this all away.
This diagram illustrates the simplified nominalist framework of the 'via moderna'. The complex intermediaries are gone. A common term is subordinated to a common concept, which directly signifies the singular things themselves.
In this nominalist view, the term 'man' is simply subordinated to a concept in the mind, and that concept directly signifies all individual men. The difference between realism and nominalism, then, is not just about whether universals exist. It is a fundamental disagreement about the structure of reality, thought, and language. It's a debate about whether semantic complexity requires ontological complexity. The realists answered yes, positing a rich world of natures and essences. The nominalists answered no, arguing that a sparse ontology of individuals is sufficient, with the complexity handled by the different ways our concepts represent them.
Conclusion
The medieval problem of universals is a deep and multifaceted debate that forces us to clarify the relationship between thought, language, and reality. It's far more than a dry scholastic dispute; it touches upon the very possibility of science, the nature of knowledge, and the structure of the world.
Key Takeaways:
- The Problem: How can we account for universal knowledge and the apparent commonality of things if the world seems to contain only particulars?
- Realism: Holds that universals are real in some sense.
- Exaggerated Realism: Universals are single entities in which particulars participate. (Largely refuted).
- Moderate Realism (Aquinas): Universals are "common natures" that exist in particulars and are abstracted by the mind.
- Nominalism: Holds that only particulars are real; universals exist only as concepts or words.
- Conceptualism (Abelard): Denies real universals but affirms universal concepts, grounded in a common "status."
- Radical Nominalism (Ockham): Universality is simply a function of mental or linguistic signs that can represent many individuals.
- The Semantic Turn: The debate evolved from a purely metaphysical question ("What exists?") to a semantic one ("How do our universal terms signify?"). The via antiqua (realist) posits complex ontological intermediaries, while the via moderna (nominalist) opts for a simpler ontology and explains differences adverbially, through the ways of signifying.
Preview of the Next Lesson:
Having established this fundamental metaphysical framework, we will remain with the towering figure of the via antiqua, Thomas Aquinas. We will move from his theory of universals to another cornerstone of his philosophy: his arguments for the existence of God, particularly his famous "Five Ways." We will see how his Aristotelian metaphysics provides the foundation for his natural theology.