Problem of universals: Meaning (information, definition, explanation, facts)

The neutrality of this article is .

There are many ways to explain what the problem of universals is briefly. Perhaps the most common way to introduce the problem identifies it with Plato's "problem of one over many." Plato's problem can be presented as follows. We observe this red rose, this red car, this red hair, and that red bird, and conclude that there is a thing that they all have in common, which for short we call "red" or "redness." But what is "redness"? There are two broad classes of view on that question, and the problem of universals is the problem of deciding which is right. The classic view of the dispute holds that there are realists (more precisely, Platonic realists) and nominalists. Realists hold that redness is a nonphysical being, called in general a universal, that stands in some relation to each red thing. Nominalists, to the contrary, hold that there is no such nonphysical being; nominalists have a variety of other explanations of why it is that we call all red things "red." The original nominalists were so-called because they held that there is nothing that all red things have in common other than the fact that they are all called (have the "name") red.

The problem of universals, then, is the problem of deciding what universals are, or are supposed to be, and whether universals exist. Universals come in a number of kinds well-recognized by contemporary philosophers. Universals, it is said, are either properties, relations, or types, but not class. It is worth noting that all four items are generally considered abstract, nonphysical entities. They are at least so considered by realists; there are others who use the terminology of properties, relations, etc., but who do not wish to be realists. Part of the difficulty, indeed, of understanding this problem is understanding the complex and confusing relations between theory and language, and what the use of language does, or does not, imply. For more introductory information explaining the basic concept of universals, see universal.

The problem and constraints on its solution

In giving a more detailed exposition of the problem, we could do far worse than to begin by asking, "What are universals supposed to be, really?" What are they in general? Given the above gloss, we are asking: "What sort of beings are types, properties, and relations, or what are they supposed to be?"

One might well compare this question to the central question of what might be called problem of substance: what are objects, anyway? As far as ontology goes, we have no other way to describe objects than by their relations to their properties and relations. If we try to determine what is meant by the question "What are objects?", ultimately we interpret that question as asking, "What are objects in relation to their properties and relations?"

In the same way, when we ask what universals are, we ask: "What are universals--abstract properties, relations, and types--in relation to particular objects?" So one might well regard the problem of universals as complementary to the problem of substance. The problem of substance has one trying to explain what objects, or substances, are in relation to universals (properties and relations); the problem of universals has one trying to explain what universals (properties and relations) are in relation to objects.

Why is this a problem? Three facts about universals, or constraints on how we think about what universals are supposed to be, will help to see what the problem is. Philosophers should be able to agree (if these constraints have been correctly stated) that, no matter what our theory of universals is, if universals really are said to exist, then our theory about universals must at least be consistent with, and even explain, these facts. In other words, we can (if they are correctly stated) take these three facts as background assumptions. Definitely we have to have some background assumptions, or else we would not have any tools to evaluate any theory of universals.

So here are the three constraints.

First constraint: universals can be multiply instantiated. Universals (if they exist) are (or can be) multiply instantiated. In other words, universals are supposed to be able to have potentially many instances; if a universal has an instance, then we say it is instantiated. For example: the type horse is instantiated by all the horses in the world. (It is a matter of considerable dispute among realists, whether uninstantiated universals exist, e.g., there might be a dispute whether the universal, flying horse, exists in spite of the fact that there are no flying horses.) So universals, whatever else we think about them, have to be the sorts of beings that can be multiply instantiated. A theory of universals has to make sense of the assumption that universals are supposed to be multiply instantiatable.

Second constraint: universals are abstract. Universals are supposed to be abstract. So, if we can form concepts of universals, then when we do, we form a concept of something abstract. In other words, when we think of, to change our example, dryness, we are thinking of something abstract. Of course, when we conceive of dryness, we might imagine a particular dry thing, like the Sahara Desert. But even though we imagine it, we understand that the Sahara Desert is not dryness itself. It is just an instance of dryness. Whenever we have an example of a universal in mind, we know very well that the example is not the same thing as the universal itself; the Sahara is not dryness itself.

Third constraint: universals are the referents of general terms. This is perhaps a very important constraint, because a very important argument infers the existence of universals from the observation that general terms seem to refer to something multiply instantiated and abstract. The general term 'red' (or 'redness'), for example, does not refer just to a particular red apple. Rather, if abstract properties exist, then the word 'redness' refers to an abstract property, not just one instance, because after all there are other instances of redness besides this apple. So if, according to a theory about universals, general terms do not refer to universals, then that theory should also hold that universals do not exist. According to this third constraint, any theory that holds that universals really do exist had better have a way for general terms to refer to universals.

There might be other constraints we might want to put on theories of universals, but these three are very common and uncontroversial.

With these constraints in mind, we can present the problem of universals as follows, a different way that, hopefully, will make it more obvious how it is supposed to be a problem:

Are there any seemingly curious beings that can be multiply instantiated, which are abstract (and which we conceive of when we conceive of abstract attributes of things), and to which general terms refer? If so, can we give any more general account of what these things are? In other words, can we give any sort of general account of what universals are, in their relation to objects, such that these three constraints about universals come out to be true?

Platonic realism

See Platonic realism. [Some text from the latter article will probably have to be copied to back this page in order to ensure some flow to this article.]

Aristotle's theory of universals

Aristotle also had a realist theory of universals, but it differed significantly in several points. See Aristotle's theory of universals.

Nominalism

Some people oppose the views of Plato and Aristotle and argue that only particular things exist. This view is called nominalism. Nominalism is the view that universals don't exist-- that is, no abstract properties, relations, or types exist.

The word "nominalism" comes from nominalis, which means, in Latin, "pertaining to names." The first nominalists said that only general terms or names exist -- no general qualities, but only their names, exist for those terms to refer to. The name "redness" certainly does exist, but there is no universal, redness, to which it refers. What does the term "redness" refer to, then? Perhaps any particular red thing, and perhaps the collection of all the red things. This is called extreme nominalism: the view that universals do not exist, and that general terms (such as "humanity" and "redness") stand for either particular objects or collections of particular objects (such as "all humans" and "all red things").

Universalists argue that there are two problems to nominalism:

• If a universal is just a name, then all that the three humans, John, Mary, and Sally have in common, is that they are called "humans." They might have the property "humanity", or the property "animal" in common. But the properties the three share is that they all have highly-developed minds; they walk on two legs; they talk; and so on; and their having these properties in common is explains why they are all called "humans.". Nominalists find it difficult to deny that things have some properties in common.
• According to extreme nominalism, general terms refer only to particular objects or collections of them. But when one talks about, for example, the redness of the apple, it is not the apple itself, but instead a property of the apple, namely its redness, that is meant. Universalists argue that denying the redness of the apple means denying the apple its "obvious" red. So extreme nominalism denies that instances of properties and relations can exist, even when it is obvious.

[Rebuttals by nominalists here]

Looking at another examples of nominalism:

• Some nominalists instead say that general terms refer to something else -- namely, images, or concepts. Imagism, to take an example, is the view that universals are mental images, pictures in the mind; or that general terms refer to such images; for example, "humanity" means a mental image of a human being, and "redness" means a mental picture of the color red. There is a very real distinction between mental images and concepts. One may imagine a thing without associating other qualities and particulars to that thing. The image is different from the concept from this point of view. This version of nominalism is called conceptualism and it is the view that universals are concepts, or that general terms refer to concepts. So triangularity itself is a concept, the concept of resembling a triangle, a closed three-sided figure. This is similar to the philosophy of Objectivism which concerns itself with how humans actually do conceptualize universals in real life. None of these philosophies are able to formulate a theory that is complete and all of them rely on base assumptions and specific beliefs to gain validity.