Problem of Universals

The problem of universals is an ancient question in metaphysics asking whether the properties that an object shares with other objects, such as color or shape, exist beyond those objects, and if so, what the nature of that separate existence would be. It traces back to Plato and Aristotle's efforts to explain the mental connections people make when recognizing that a property such as shape or color is the same across nonidentical objects: if every cup holder is circular, for instance, circularity appears to be a single universal property shared by many distinct things, and a set of ten balls of only two colors seems to involve just two universal color properties despite comprising ten separate objects. Philosophers broadly agree that people can talk and think about such universals, but they disagree sharply over whether universals exist in reality beyond mere thought and language.