Problem of universals

Many things look the same.

They might be red or round. Do these shapes exist on their own?

Some people think they do. Others think they are just in our minds. This is a big question. A universal is a trait shared by many things. For example, many cups are round. Some thinkers say "roundness" is real. They believe it exists even without the cups. Other thinkers say it is just a word. They think it only lives in our thoughts. We use these ideas to group things together.

Have you ever wondered about shared traits?

Many things share qualities like color or shape. A universal is a trait found in many things. For example, many cup holders are circular. Circularity is a universal property. Many people think about whether these traits are real. Do they exist on their own? Or are they just in our minds?

Ancient thinkers had different ideas. Plato believed in a world of forms. He thought these forms were the real world. To him, objects we see are just like shadows. Aristotle was his student. He disagreed with Plato. He thought universals were part of the things themselves. For him, an oak tree has "oakness" inside it.

Later, thinkers like Boethius studied this. Boethius said the mind can think about traits in a special way. Other thinkers, called nominalists, had a different view. William of Ockham was a famous nominalist. He argued that universals are just words or ideas. He believed they only exist in the human mind. They do not have a real place in the world.

Have you ever noticed how many different things can share the same trait?

A universal is a quality or a relation found in two or more things. For example, if many cup holders are circular, circularity is a universal property. You might also see this with people. If two daughters are both female offspring of a man named Frank, then being female is a universal trait for them. Philosophers agree that humans can talk and think about these shared traits. However, they disagree on whether universals truly exist in the real world. Some wonder if these qualities exist beyond our own thoughts and speech.

This big question is part of a field called metaphysics. It asks if properties like color or shape exist separately from the objects that have them. One way to look at this is through predication. This is a way of using terms to describe things. For instance, a philosopher might say "man" is a universal term. This is because it can describe many different people. On the other hand, a name like "Callias" is a singular term. A singular term only describes one specific individual. This helps thinkers organize how we describe the world around us.

Ancient thinkers like Plato and Aristotle explored these ideas deeply. Plato believed in a world of perfect forms. He thought the objects we see are just imperfect shadows of these real forms. To Plato, true knowledge only comes from understanding these eternal forms. Aristotle was a student of Plato, but he had different ideas. He believed universals were part of the natural world itself. He thought an oak tree has "oakness" as a part of what it is. This helped him study how living things work in nature.

In the Middle Ages, thinkers like Boethius studied these problems further. Boethius suggested the mind can separate ideas in thought. This means we can think about a trait even if it is not separate in reality. Other thinkers, called realists, believed universals were real entities. For example, Duns Scotus argued that properties like redness exist in reality. But there were also thinkers called nominalists who disagreed. William of Ockham was a famous nominalist from the 1300s. He argued that universals are just words or concepts in the mind. He believed they have no real place in the outside world.

Many different views have emerged from this long history of wondering. In the 1800s, Georg Wilhelm Hegel said universals and particulars depend on each other. This means one cannot exist without the other. John Stuart Mill also thought about how we identify things. He suggested we sometimes focus only on the traits needed to identify a person. Later, Charles Sanders Peirce suggested that general laws are real parts of the world. Even today, people still use these ideas to understand logic and knowledge. It is a puzzle that keeps many thinkers busy.

The problem of universals is a central question in metaphysics. Metaphysics is the branch of philosophy that studies the nature of reality. This specific problem asks about the status of shared properties. If two objects share a color or a shape, does that property exist independently?

Philosophers wonder if qualities like "redness" or "circularity" exist beyond the objects themselves. A universal is defined as a quality or a relation found in two or more entities. For example, if every cup holder is circular, circularity is a universal property. Universals help humans make mental connections between nonidentical objects. While philosophers agree we can think about universals, they disagree on their actual existence.

Ancient philosophers explored this through a process called predication. Predication involves using terms to describe the characteristics of a subject. In his work *Categories*, Aristotle explained this using universal and singular terms. A universal term, such as "man," can be predicated of many individuals. A singular term, such as "Callias," refers to only one specific person. This distinction helps organize how we describe the structure of the natural world. By studying these terms, thinkers attempt to understand the intelligible order of the world. This process is vital for logic and epistemology, which is the study of knowledge.

Plato and Aristotle offered very different views on these properties. Plato believed in a sharp distinction between two worlds. He argued that the world of perceivable objects is imperfect and changing. In contrast, he believed in a world of eternal Forms, or *eide*. For Plato, true knowledge only concerns these unchanging Forms. He viewed the sensible world as mere shadows of the real world of Forms. This view is known as Platonic realism. However, some critics, like Diogenes of Sinope, challenged this idea. Diogenes famously noted that he could see Plato's cups, but not "cupness."

Aristotle disagreed with his teacher, Plato, regarding the location of these forms. He transformed Plato's ideas into "formal causes." These are the essences or blueprints of individual things. Aristotle focused on the natural world and its many living beings. He believed that a universal is a part of the individual thing. For instance, an oak tree possesses "oakness" as part of its nature. This makes Aristotle a moderate realist. He believed we can gain knowledge of the sensible world through observation. This approach helped establish him as a founder of induction.

During the Middle Ages, the problem was introduced by the philosopher Boethius.

Boethius studied how universals relate to particulars. He argued that a universal must be present in each particular simultaneously. He also noted that a universal must be present in an identical manner. Boethius proposed that the human mind can abstract these qualities. The mind can separate a concept in thought even if it is not separate in reality. This allowed him to avoid the extremes of Platonic realism and pure mental construction. He suggested universals are the mind thinking about particulars in an abstract way.

Medieval philosophy saw a rise in both realism and nominalism. Realists like Thomas Aquinas and Duns Scotus argued for the reality of universals. Aquinas believed the essence and existence of a thing were distinct. Duns Scotus argued there is only a "formal distinction" between them. Scotus believed properties like redness exist as mind-independent entities. On the other hand, nominalists argued that universals are merely verbal constructs.

The philosopher Roscellinus claimed universals were just vocal utterances. William of Ockham was a prominent nominalist in the 14th century. He argued that universals are products of human thought and language. To Ockham, nothing outside the soul is truly universal.

In the 19th century, new perspectives emerged from different thinkers. Georg Wilhelm Friedrich Hegel proposed a dialectical relationship between universals and particulars. He suggested that one cannot exist without reference to the other. John Stuart Mill discussed how we identify objects by certain attributes. He noted that we might focus on attributes necessary to identify a man. Charles Sanders Peirce, the father of pragmatism, offered another view. He argued that if a mental fact works in practice, it functions as a universal. Peirce also believed that "Thirdness," or general laws, are extra-mental realities. These diverse views continue to shape how we understand the relationship between thought and the world.