Universals in Thought
We introduce the concept of the particular because we observe distinctness in the world. We introduce the concept of the universal because we observe similarity in the world. I see the cat as distinct from the computer and I conclude that particulars exist; if I didn’t I wouldn’t have much use for the concept of a particular. But I also see that several particulars are similar to each other and I conclude that there are respects of similarity, which I call universals; if I didn’t I wouldn’t have much use for the concept of a universal (suppose I live in a world without similarity). Thus the particular-universal distinction finds a foothold in our description of the perceptible world, from which it might fruitfully migrate: we use it in our general conception of the nature of objects. We might say that it explains what we observe: we see distinctness because particulars exist, and we see similarities becauseuniversals exist. We describe the world as consisting of particular objects with shared properties (attributes, features, qualities, characteristics, forms). Evidently this is a sensible way to proceed, even if we subsequently disagree about what particulars and universals are (are particulars sets of universals or are universals sets of particulars?). But it is also true that we describe thoughts using the same distinction: they have a role in psychology as well as in ontology. For thoughts are about particulars and also about universals: the same duality pervades the mental world as the non-mental world. Why do we talk and think this way about thoughts? Why, in particular, do we think that thoughts have something in common analogous to universals—with the very same entity cropping up in different thoughts? It isn’t that thoughts instantiate universals as objects do (they are not red, square, etc.), so the rationale cannot be the same in both cases; we certainly don’t see that distinct thoughts share the same universal. So what is it that explains our readiness to postulate identity of universals across distinct thoughts? Hugely many different individual thoughts can concern the same universal—or so we suppose—so why do we insist that it is the same entity that crops up in each case? And why must this entity approximate to Plato’s conception of a universal? Why are universals considered an indispensable part of psychology?
First, let us note the troubles of theories that try to do without them. Suppose we limit ourselves to particulars of various sorts—mental, linguistic, or even immaterial. Then we run up against the problem that we can’t capture the identity of the thought from one instance to another: I can’t think the same thing of two objects when I think that both are red, say. For the particulars in question will vary from instance to instance, according to time or person. If we try to circumvent this problem by appealing to types of particular, then we are back with universals. The general concept can’t be equated with a series of particular happenings; we need something in common between all the cases. We need, that is, the universal RED. Sameness of ascribed property means sameness of property ascribed. We need something abstract and general to capture the commonality across thoughts. Nor will it help to bring in dispositions, since these vary over time depending on external circumstances and the thinker’s internal psychology. My disposition to use “red” in a certain way at time t need not be preserved to a later time at which I use the same word, despite the fact that I ascribe the same property at the later time. Dispositions to behave in certain ways don’t track meaning or attribute denoted, so they can’t play the role of universals as traditionally understood. We need the robust identity provided by a traditional universal to explain how the same thing can be thought about different things, or about the same thing at different times. But why exactly do we need the same universal at any occurrence of the thought, so long as some universal is present? It can’t be a dated particular or a changing disposition, but why do we insist on invoking the very same universal whenever language appears to suggest it? Why must “red”, say, always be assigned the same universal? Couldn’t this be some sort of oversight or result of laziness? Why don’t we follow the example of “bank” and assign different universals in different contexts? True, that would be contrary to common sense, but it would be nice to know if the usual practice has anything further to recommend it. Why are we so wedded to the idea of universal invariance as between different thoughts and sentences? Why not a more anarchic approach?
The answer is that logical reasoning requires it. Consider the classic example: All men are mortal; Socrates is a man; therefore Socrates is mortal. We have all been taught that for an argument to be valid there must be no equivocation in the premises and the conclusion. Thus the name “Socrates” must have the same meaning in the conclusion as it has in the second premise, i.e. it must designate the same particular. But the same is true of the predicates, and this requires that “mortal” must have the same meaning in the conclusion that it has in the first premise. That in turn requires that the same universal be assigned to it not some distinct universal (e.g. being vegetarian). So validity depends on constancy of universals through premises and conclusion. We can bring this out be rephrasing the argument using nominative forms: Anything that has humanity has mortality; Socrates has humanity; therefore Socrates has mortality. What we call a universal is just whatever is needed to render this argument valid, which it clearly is: it must not vary between premises and conclusion, as associated particulars and dispositions will. Thoughts occur in trains of logical reasoning and we need entities that will respect the prohibition on equivocation. Thus universals come into the psychological picture; they don’t just belong to the non-psychological world. They have a kind of double life, being related both to similarity among particulars and to validity of argument: we need them in both domains. Again, what they are exactly remains to be determined, but we can’t do without them in some form if we want to make sense of object similarity and argument validity. Postulating them is not some sort of gratuitous mysticism or ontological indulgence; it is warranted by facts that need explaining—the existence of similarity and logical validity. There cannot be logic without something like Plato’s universals, i.e. something constant across particular sentences or thoughts. This means that general concepts cannot be characterized without reference to universals. When we employ concepts we re-apply the same universal over time, which is what happens in a sequence of thoughts that form a logical argument. Token thoughts therefore share universals as particulars share universals—the former by means of intentionality, the latter by means of instantiation.
 The word “universal” is not ideal, entrenched as it is, since so-called universals are not universal—not all things have them. Not all things are red or square or even or good, only some are; so what are called universals are really partials, parochials. But there is no natural term that conveys the idea accurately: the closest I can find would be “shareables”, but that is not a felicitous expression. So we may as well stick to “universals” noting that the things in question are precisely not universally distributed. Notice too that the term “particular” is also not particularly descriptive and must be used in a technical sense: how “particular” is a grain of sand? These are both technical terms (not that there is anything wrong with that).