Trope theory offers an alternative to both universals and nominalism. Rather than postulating universal properties that multiple objects share, tropes are abstract particulars unique to each concrete object. Each object has its own redness, roundness, etc. This offers a nominalist-friendly ontology without committing to universals.
Contrast with universalism and nominalism. Work through how trope theory explains property sharing, resemblance, and predication. Consider the costs and benefits of multiplying abstract entities.
That tropes are identical to concrete properties of objects. That trope theory requires believing in more abstract entities than universalism. That resemblance between tropes is mysterious or unanalyzable.
From universals-and-particulars and trope theory, you have both positions on the table. Universals are properties that can be genuinely shared by distinct objects: when two red balls are both red, they literally instantiate the same entity — the universal redness — which is wholly present in each. Tropes are property-instances: abstract particulars that belong to exactly one object. Each red ball has its own redness-trope, and those two tropes are numerically distinct entities even if they are qualitatively identical. The central question dividing the theories is not whether properties exist, but what the metaphysical structure of property-sharing turns out to be.
The universals theorist offers a clean account of property-sharing: when two things are both red, they share a single entity. The trope theorist says: they each have their own redness-trope, and property-sharing is a matter of resemblance between distinct tropes rather than identity of a shared entity. This shifts the explanatory burden. Instead of explaining resemblance in terms of shared universals, the trope theorist takes resemblance between tropes as the ground for our property-talk. Things count as being the same color because their respective color-tropes resemble each other maximally; a resemblance class of exactly-resembling tropes plays the role that a universal would play in the competing theory.
How does trope theory compare to strict nominalism? A strict nominalist about properties says two red things have nothing literally in common — "red" is just a general term we apply to similar-looking things, full stop. Trope theory is a middle path: tropes are abstract (they are "thin" — just the property, not the whole concrete object) but particular (each belongs to exactly one object). This gives trope theorists more ontological resources than strict nominalists — they can say that a thing's redness is a genuine entity — while avoiding the universalist's commitment to entities that must be multiply located.
The key advantage trope theory claims over universalism is avoiding the problem of immanent universals: if universals are "in" the objects that instantiate them (rather than in a separate Platonic realm), how can a single entity be wholly present in two objects that are spatially separated? Tropes sidestep this entirely — each object has its own trope, and nothing needs to be in two places at once. The key advantage over strict nominalism is explanatory: when two red things resemble each other, the trope theorist can cite the resemblance between their respective redness-tropes as the metaphysical ground for that claim, rather than leaving resemblance as a primitive with no further analysis. The cost is that the resemblance relation between tropes must itself be explained, and circularity threatens — a challenge the trope theorist must handle carefully.
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