Two fire trucks and an apple are all red. A realist and a resemblance nominalist are asked what makes these three things share the property of redness. Which pair of answers best captures their positions?
ARealist: 'They all cause the same experience in normal perceivers.' Nominalist: 'They all reflect the same wavelengths of light.'
BRealist: 'There is a single entity, redness, wholly present in each of them.' Nominalist: 'They sufficiently resemble each other and the paradigm cases of red things.'
CRealist: 'They belong to the same natural kind.' Nominalist: 'They are classified together by our linguistic conventions.'
DRealist: 'Redness is a concept in our minds that we apply to them.' Nominalist: 'They each have their own individual redness that is distinct from the others.'
Realism holds that universals are real entities wholly present in each instance — the single property redness literally exists in each red thing. Resemblance nominalism denies this, instead explaining similarity through resemblance: two things are red because they sufficiently resemble each other and paradigm red objects, without any shared universal. Option D partially describes trope theory (individual property instances) and a form of conceptualism (redness as a mental concept), neither of which captures the standard realist-nominalist divide.
Question 2 Multiple Choice
Resemblance nominalism faces a circularity objection. Which formulation best captures the problem?
AIt cannot explain how we learn color terms as children
BTo say two things resemble each other is to say they share a property — which smuggles a universal back in through the back door
CIt requires an infinite regress of resemblance relations
DResemblance is itself a universal that must be explained, causing the nominalist's position to be self-refuting
The Explainer states this directly: 'What grounds the resemblance relation? If we say two red things resemble each other, are we smuggling in a shared property through the back door?' When you say two things 'sufficiently resemble each other with respect to color,' you seem to already be invoking a shared color property — the very universal the nominalist was trying to eliminate. Option D (the resemblance-universal regress) is related and sometimes cited, but the core objection is the one in option B: explaining similarity through resemblance seems to presuppose similarity.
Question 3 True / False
Aristotelian realism holds that universals like redness exist even if hardly anything in the world is currently red.
TTrue
FFalse
Answer: False
This describes Platonic realism, not Aristotelian realism. The Explainer distinguishes them explicitly: 'Platonic realism places universals in a realm of abstract objects that exist independently of any particular instance; redness exists whether or not anything is currently red. A more moderate Aristotelian realism holds that universals are real but only ever exist instantiated in particulars — redness exists only insofar as there are red things.' The contrast between these two forms of realism is itself an important internal divide within the realist camp.
Question 4 True / False
Trope theory avoids both Platonic abstract universals and the circularity objections facing resemblance nominalism.
TTrue
FFalse
Answer: True
Tropes are particular instances of properties: the redness of this apple is a distinct entity from the redness of that fire truck, even if they resemble each other. This avoids Platonic universals (there is no single abstract redness existing apart from instances) while also giving properties genuine ontological status — unlike class nominalism, which identifies properties with sets. Resemblance nominalism still needs to explain what grounds the resemblance between tropes, but trope theory at least avoids positing a shared universal while still individuating properties.
Question 5 Short Answer
What is the core problem that the debate between realism and nominalism is trying to solve, and why does it matter beyond abstract metaphysics?
Think about your answer, then reveal below.
Model answer: The core problem is explaining what grounds objective similarity among particulars — what makes two red things both genuinely red, rather than merely called red by convention. This matters beyond abstract metaphysics because the answer shapes the theory of natural laws (do laws hold because universals necessitate causal relations?), the status of mathematical objects (are numbers universals?), and the metaphysics of science (what makes something a natural kind rather than an arbitrary grouping?). Choosing between nominalism and realism is one of the first and most consequential decisions in constructing an ontology.
The problem of universals is not just a puzzle about language or classification — it has downstream consequences for whether we think the world has objective structure independent of our categories. A realist can say that natural kinds like 'water' or 'electron' carve nature at its joints because the relevant universals are really there; a nominalist must find another way to distinguish natural kinds from arbitrary groupings. This is why the debate, despite seeming abstract, remains central to philosophy of science and metaphysics.