Universal

The 14th-century dispute between Ockham's nominalists and Scotus's realists wasn't just ivory tower philosophy—it split universities, influenced theology, and even affected legal thinking about corporate entities. Ockham's razor, cutting away universals as unnecessary entities, helped birth modern empiricism and scientific method. When you hear someone say "don't multiply entities beyond necessity," you're witnessing this medieval debate echoing through time.

Plato introduced universals (his Forms) as a kind of philosophical escape room: how do we know that two beautiful things share beauty when every beautiful thing eventually fades? His answer—an eternal, perfect Form of Beauty existing beyond physical reality—wasn't just metaphysics but a psychological coping mechanism for mortality. The universal becomes literally more real than the particulars we touch and see, flipping our entire sensory relationship with reality.

Modern intellectual property law wrestles with the universal-particular problem constantly: is Mickey Mouse a universal that exists across all instances, or just a collection of particular drawings and performances? Courts must decide whether similarity between works reflects shared access to a universal "idea" (not copyrightable) or copying of particular "expression" (protected). This ancient metaphysical puzzle literally determines billion-dollar lawsuits and what you can legally create.

Nelson Goodman's 1955 "grue" paradox weaponized universals against themselves: imagine "grue" means green until 2030, then blue afterward. All emeralds are grue and green—but which universal better predicts the future? This thought experiment revealed that our choice of universals isn't just discovered but involves implicit commitments about similarity and projection. It fundamentally shook confidence that science simply "carves nature at its joints."

AI image classifiers are essentially building universals from particulars: fed thousands of cat photos, they extract what makes a cat a cat. But they're discovering what Aristotle suggested—universals emerge from particulars rather than existing separately. When your phone recognizes faces, it's performing empirical abstraction, creating usable (if imperfect) universals from experience. The debate has moved from "do universals exist?" to "which statistical patterns count as meaningful categories?"

Buddhist philosophy largely rejects universals as part of rejecting all fixed essences—there's no universal "chairness," just particular arrangements we find useful to sit on. This isn't just metaphysical housecleaning but a therapeutic technique: much human suffering comes from expecting people, relationships, or situations to conform to our mental universals. When you're frustrated that your friend "isn't being a good friend," you might be trapped by a universal that exists only in your expectations, not in the irreducibly particular reality before you.