Philosophy
The Metaphysics of Properties and the Problem of Universals
Quick fact
The problem of universals has been debated for over 2,000 years, from Plato's theory of Forms to modern trope theory, and it remains one of the deepest puzzles about the structure of reality.
Why this is interesting
You see two red roses. You know they are both red. But what is that 'redness' they share? Is it a thing that exists somewhere, or just a name we give to similar experiences?
Read the full explanation
Understanding The Metaphysics of Properties and the Problem of Universals
Imagine you have two apples, both bright red. You naturally say they share the property of redness. But what does 'sharing' mean? Where is this 'redness'? Is it a thing that exists in both apples at the same time? Or is it just a word we use to group similar colors? This is the problem of universals. Philosophers have proposed three families of answers: - Realism: Universals are real, mind-independent entities. Plato believed in a realm of perfect Forms, where the Form of Redness exists permanently, and each red object 'partakes' in it. This explains why different objects can be the same color. - Nominalism: Only particular objects exist. There is no such thing as 'redness' in general—only red apples, red cars, red stop signs. We group them because of similarities, but the grouping is just a human convention. This avoids positing mysterious abstract entities. - Trope theory: A middle path. Properties are not universal and repeatable, but each instance of redness is a particular—a 'trope'. This apple has its own redness-trope, that apple has a different but exactly similar redness-trope. This captures the intuitive reality of properties without positing a shared universal.
A deeper explanation
The debate centers on two fundamental problems: the one-over-many and the resemblance problem. The one-over-many problem: Why do two distinct objects both 'have' the same property? If there is a universal 'Redness', it exists as a single entity that is wholly present in each red object. That explains why they are both red—they share the same universal. Without universals, we must explain similarity without identity of property. The resemblance problem: How do we explain that objects are similar? Nominalists often say they resemble each other, but that resemblance must itself be a property, leading to a regress. If we say two apples are both red because they resemble each other, we need an account of that resemblance, which might require another property, and so on. Realism faces its own challenges. If universals exist, where are they? Are they in space and time? Plato's theory places them in a separate realm, which many philosophers find problematic. Also, if a universal is wholly present in multiple locations, that seems to violate our ordinary ideas about identity. Trope theory avoids these issues by making properties particulars. Each apple has its own redness-trope. They are exactly similar, but not identical. This accounts for both the reality of properties and the diversity of individuals. It also handles the problem of resemblance: tropes are similar by their nature, not by a further property. This debate matters because it underpins our understanding of laws of nature, causation, and scientific kinds. If universals exist, laws can be understood as relations between universals. If only particulars exist, laws must be regularities among individuals. Thus, the metaphysics of properties has direct consequences for philosophy of science and epistemology.