Nominalism is the idea that only specific, real things—like your dog, your pencil, or your friend—actually exist, and that general words we use, like “animal,” “red,” or “smart,” are just names we made up to talk about things that seem similar. These general words are called universals, and the real, individual things we can see and touch are called particulars.
A Nominalist believes universals don’t exist out in the world; they’re just useful ways of grouping stuff in our minds or in language. For example, if we call both a cherry and a stop sign “red,” a Nominalist would say there’s no magical “redness” floating around that they both share—we’re just noticing a resemblance and using the same word.
Some Nominalists explain this by saying we group things by how much they resemble each other, while others say the group itself—a class—is all that matters. What’s important is that they all agree universals like “beauty” or “circle-ness” aren’t real things on their own.
This matters because it helps us think more clearly about what’s real and what’s just a label. It also makes us ask: when we use big ideas like “truth” or “justice,” are we talking about real things or just ways of organizing the world in our heads? Nominalism says: it’s probably just the way we talk.