Subject and Predicate

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The contrast between "subject and predicate" is a significant one in at least four different realms of discourse: grammar, epistemology, logic, and metaphysics. A large number of philosophical problems have to do with how the distinction on one level is related to that on some other level; whether there really are four such distinct realms and, if so, how they bear on one another are matters of controversy.


In the realm of grammar, subject and predicate are sentence parts; they are, therefore, words or groups of words, and their definition and identification is a matter of syntax. In the simplest case, where the sentence consists of just two words, such as
(1)      Bats fly,
(2)      Fraser swims,
the subject is the noun and the predicate is the verb. Very few sentences are so simple, but an indicative sentence with just one noun and one verb remains a good paradigm for the grammatical categories of subject and predicate because we can see in it the form of the sentence stripped down to its essentials: If either of the two words were omitted, we would no longer have an indicative sentence. Furthermore, very many sentences of English, as well as of other familiar European languages, break neatly and obviously into two parts corresponding to the noun and the verb in the paradigm, and modern linguistic analysis of sentence syntax generally begins by viewing a sentence as a noun phrase plus a verb phrase:

Although subject-predicate sentences are very common in English and in other languages, this form of sentence is not the only one, other forms being exemplified in English by normal idiomatic expressions for commands, requests, salutations, and so on. These other forms of sentence, however, have traditionally been assimilated to the subject-predicate form through the assumption of an "unexpressed subject" or some other missing element. It once seemed reasonable to try to save appearances in this way because subject and predicate seemed to be universal grammatical categories, found not only in the European languages but also, for example, in Sanskrit. Recent familiarity with a wider variety of languages has shown that these categories are by no means universal, and it is doubtful whether any grammatical categories or linguistic forms are universal. Some linguists have proposed that topic and comment are found universally, although subject and predicate are not. These categories, however, do not have to do just with the arrangement of words in sentences but rather with knowing what is being discussed and understanding what is said about it; hence topic and comment are not purely grammatical categories. The present situation in linguistics may therefore be summed up by saying that subject and predicate are useful grammatical concepts but do not represent universal grammatical categories.

In philosophy the grammatical distinction between subject and predicate has been prominent at least since Plato, who, in the Sophist, distinguished nouns and verbs as two classes of names. It is fair to say, however, that in that discussion, as well as in subsequent ones, philosophers have been interested in this grammatical distinction primarily because of the use they might make of it in treating problems of epistemology, logic, and metaphysics.


In epistemology the contrast between subject and predicate is a contrast between that part of a sentence which serves to identify or designate what is being discussed and that part which serves to describe or characterize the thing so identified. The categories of subject and predicate have more claim to universality at the level of epistemology (semantics) than at the level of grammar (syntax). It is here that the hypothesis about topic and comment, mentioned earlier, has its significance, for the fact that every language has some grammatical device or other for identifying a subject, or topic, and predicating something of it, or commenting on it, largely accounts for our remarkable ability to translate the content of any message from one language into another.

The epistemological sense of subject and predicate has much in common with the grammatical sense: Sentences (1) and (2) can be taken as paradigms for both senses, and the grammatical subject very frequently identifies the subject of discourse. Nevertheless, the two senses are not identical. They diverge, for example, in sentences with a dummy subject. In "It is raining" the expletive "it" is the grammatical subject of the sentence, but since it does not designate anything at all, it does not designate or identify what the sentence is about. Other instances are more relevant to philosophical issues and may be controversial. Consider
(3)       What is not pink is not a flamingo.
(4)      What is not just is not to be done.
There is no difficulty with (4), for it says something about unjust acts, and hence its grammatical and epistemological subjects coincide. But (3) seems to be about flamingos rather than about nonpink things, even though it has the same grammatical form as (4). Perhaps this is because we directly recognize and classify things as flamingos and as unjust acts, and even as pink, whereas in order to call something "not pink" one would normally first recognize it as gray or blue or some other color. If this is correct, the epistemological subject of (3) is mentioned in the grammatical predicate rather than in the grammatical subject.

Another instance of the divergence of the epistemological and grammatical senses is in relational sentences, such as
(5)      Andrew was hit by Bernard.
(6)      The cat is between the bird and the snake.
Sentences (5) and (6) may be taken to be about the two persons and the three animals, respectively, and what is said about their epistemological subjects is that a certain relation is true of them. Treating (5) and (6) as having multiple subjects in this manner is much more congenial than is a grammatical analysis to what Bertrand Russell, among others, said about the importance of relations.

It should be noted that what counts as the epistemological subject of a statement may be determined in part by the context in which it is made: If Bernard is the "topic" of conversation, (5) would naturally be construed as a "comment" about him, but other conversations in which (5) occurs will be focused differently. The importance of context in determining what counts as a subject differentiates the epistemological conception of subject from all the others.

Predicates as well as subjects have required special treatment in epistemology. Immanuel Kant distinguished real predicates from grammatical or logical predicates, a real predicate being one that says something about the subjectthat is, one which attributes some property to the subject. Kant's contention that "exists" is not a real predicate but only a grammatical or logical one provides the basis for his refutation of the Ontological Argument. Statements of identity have also been held by Gottlob Frege, Russell, Ludwig Wittgenstein, and others not to be genuine predicationsor at least not to be straightforward ones. Hence, in
(7)      Tully is Cicero
the words "is Cicero" would not express an epistemological predicate, although they assuredly constitute the grammatical predicate. These are matters that are still not so clear as they might be.

Some very important topics in semantics and the philosophy of language are connected with the epistemological contrast between subject and predicate. In order to know what a person is talking about, I must know to what (or to whom) certain words in his utterances refer; the problem of how words can have such reference is an important one. In order to understand what is said about the subject under consideration, I must further know what is signified or entailed or meant by certain other words the person uses, whence arises another important problem, how words come to have sense or connotation. The distinction between two such modes of meaning, characteristic respectively of subjects and of predicates, has a long history and is still a live issue. Plato, in the Theaetetus and the Sophist, distinguished the mode of meaning of nouns from that of verbs. More recently J. S. Mill's distinction between connotation and denotation and Frege's distinction between sense and reference have taken up the same theme and made it central to the philosophy of language.


In formal logic there has been a distinction between subject and predicate ever since Aristotle's pioneering work in the field, but a dispute about the nature and scope of the distinction separates traditional from modern logicians. Aristotle would regard sentences (1) and (2) as both having subject-predicate form, but only (1) could serve as a paradigm for his formal logic. In traditional formal logic what is important about the subject term in the paradigm is, roughly, that it comes at the beginning of the sentence and indicates what (or who) is being discussed and that its quantity can be expressed by "some" or "all" preceding the noun. The pattern involved is
S is P,
and since every proposition must have a topic about which something is asserted, this pattern is held to be manifested universally in categorical propositions. In modern logic, on the other hand, what is important about the subject term is that it is a proper name and stands for an individual, and so only sentence (2) can serve as a paradigm of the subject-predicate form. The pattern involved is
(where "F " stands for some attribute and "a " is a proper name); this pattern never applies to general propositions, since fully general propositions contain quantifiers, variables, and predicate terms but no proper names. According to this view general propositions pertain just to predicates and are not subject-predicate propositions at all. Russell's famous attack on "subject-predicate logic" was an attack on the view that every proposition must have a logical subject.

From a formal point of view the issue can be seen as a dispute about whether the principle of transposition (or contraposition) applies to subject-predicate propositions. In traditional logic it does, for the complement of a predicate can serve as a subject. This is not the case in modern logic, however, where only singular terms count as subjects and where transposition applies only to complex propositions compounded with the "if-then" sentence connective. There is a related divergence in the treatment of existence. Kant, a typical traditional logician in this respect, called existence a "logical" predicate, although not a "real" one; in effect, the grammatical analysis of assertions of existence into subject and predicate is carried over into logic. In modern logic, on the other hand, existence is generally represented through quantification, rather than through a predicate.

Epistemological and metaphysical considerations are involved in this dispute about how to represent subjects and predicates in formal logic. Roughly speaking, traditional logic seems to favor some sort of realistic view of universals, since terms representing universals can serve as both logical subjects and logical predicates. In the notation of modern logic, on the other hand, only singular expressions can serve as logical subjects, and this rule seems to give prominence to individuals rather than to universals. But a variety of epistemological and metaphysical views can consistently be advanced by both traditional and modern logicians, and the ascendancy of modern logic can be attributed to its greater flexibility, adaptability, and power as a calculus, rather than to epistemological and metaphysical views associated with it. It seems prudent, therefore, to keep matters of perspicuous symbolism and logical transformation separate from other considerations.

To illustrate the problems about the relation of logical structure to epistemological structure, one might consider
(8)      All ravens are black.
The epistemological subject of (8) is ravens, and hence one would go about confirming the proposition by examining ravens and finding them black. If, using the rule of transposition, we derive from (8) the logically equivalent form
(9)      All nonblack things are nonravens,
one is tempted to assume that the epistemological subject and predicate of (8) have been similarly transposed, so that nonblack things is the epistemological subject of (9). This assumption gives rise to the so-called paradox of confirmation, for it then appears as though we might confirm (8) and (9) by examining nonblack things and finding them not to be ravens, contrary to our normal procedure for confirming such simple generalizations. One solution is to hold that transposition does not apply to the epistemological structure of a proposition, that the epistemological structure of a proposition is therefore not always parallel to its logical structure, and that the epistemological subject of (9) is the same as that of (8)that is, ravens. But the desire to have epistemological structure unambiguously represented in logical notation is a powerful consideration for some philosophers, and hence the matter is still controversial.


The distinctions between subject and predicate in grammar, epistemology, and logic have given rise to a variety of metaphysical doctrines. These doctrines deserve separate consideration because although they are closely related to the distinctions already sketched and are suggested by them, none follows from them.

Plato noted that applying different predicates to a subject often entails a change in the subject, whereas applying a predicate to different subjects does not entail a change in the predicate. He took this changelessness to be a mark of reality (as well as epistemological priority), and hence his theory of Forms gives great ontological prominence to predicates (concepts, universalsi.e., that which a grammatical predicate stands for). This bold thesis opened a long and continuing dispute about the nature of universals, the problem being to determine what ontological commitments, if any, are entailed by our use of predicative expressions (in the epistemological sense).

Aristotle, in contrast to Plato, gave ontological standing to subjects as well as to predicates. Discussing substance in his Categories, he defined "first substances" as things satisfying two conditions: (a ) being subjects but never predicates and (b ) not being in or of something else (as a color or surface must be the color or surface of some other thing). He then defined "second substances" as things satisfying the second condition but not the first. First substances are individuals. Second substances are species or universals and hence incorporate an element of Plato's metaphysics (although not all universals are substances). An attractive feature of Aristotle's metaphysical treatment of subjects is that it fits his conception of subjects in epistemology and logic: What we talk about and investigate (especially in biology, Aristotle's scientific forte) are individuals and species, and his logic allows both individual names and universal terms, including species names, to occur as logical subjects. But, in spite of its merits, Aristotle's metaphysical conception of subjects is often regarded as unsatisfactory, largely because of qualms about putting individuals and species in one basket, about distinguishing predicates that stand for substances from those that do not, and about the usefulness of traditional logic.

Gottfried Wilhelm Leibniz's doctrine of monads builds on Aristotle's conception of individual substance. But Leibniz considered Aristotle's definition inadequate, and he defined a monad or individual substance as a subject that contains all its predicatesthat is, as an individual from whose "notion" it is possible to deduce all that may ever be truly predicated of it. Few philosophers have thought there were any such substances. One difficulty may be that Leibniz attributed to his monads, which are epistemological subjects, the sort of identity that characteristically belongs to a predicatenamely, a definite set of entailments that define it.

Whereas Leibniz had only one kind of substance, G. W. F. Hegel allowed only one individual substance, the Absolute. The Absolute is the ultimate subject of every statement and resembles Leibniz's monads in that it contains all its predicates in the same sense as the monads are supposed to. Other philosophers have not been convinced of the existence of such a universal subject; Russell, who acknowledges Hegelian idealism to be a plausible account of the metaphysical implications of traditional logic, regards the doctrine as a reductio ad absurdum argument against a logic that analyzes every proposition as having a subject and a predicate.

Another interesting element of idealism is the concept of the concrete universal. Like the idea of a monad, this concept is an attempt to overcome the subject-predicate dualism by amalgamating features of both subjects and predicates in a single sort of entity. Whereas a monad is a subject with characteristics of a predicate (in that its identity is determined by what is logically contained in it, or entailed by it), a concrete universal is a predicate treated as a concrete individual thing.

One philosopher who accepted the subject-predicate dualism as a basis for his metaphysics was Frege. There are, he maintained, two radically different sorts of things, objects and concepts. Objects are complete, or "saturated," and stand on their own, so to speak; we have names for them and talk about them, but the name of an object can never be a grammatical or logical predicate. Concepts, or, more generally, what Frege called "functions," are incomplete, or "unsaturated"; they require an object to complete them and hence cannot stand alone, and a concept term is always a predicate, never a subject. Frege's dualistic view has been very influential with other philosophical logicians, including Russell, Wittgenstein, Rudolf Carnap, and P. T. Geach, but difficulties in Frege's formulation of it have impeded its general acceptance.

One difficulty is that even Frege wished to talk about concepts, and hence he had to suppose that each concept has a special object associated with it that serves only as an object to talk about when we mean to discuss the concept. A more serious difficulty is that the object-concept dualism does not fit with Frege's semantic distinction between sense and reference, which also arises from a consideration of subjects and predicates. One might expect that reference would be the mode of meaning characteristic of names of objects, and sense the mode of meaning characteristic of concept terms; however, both names and concept terms have both sense and reference. Frege had powerful reasons for what he said, but the final impression is that his two distinctions are distressingly unrelated; hence, the philosophers most influenced by him have differed from him. Russell, for example, vigorously rejected Frege's distinction between sense and reference (in his essay "On Denoting"), and Wittgenstein in his Tractatus Logico-Philosophicus, although indebted to Frege when he characterized his metaphysical objects, left no room for any other entities corresponding to Fregean functions.

Many analytic philosophers (which included Carnap, Ernest Nagel, and Max Black) hold that neither grammatical nor logical categories have metaphysical implications. P. F. Strawson, however, revived the issue among them by considering the implications and presuppositions of grammatical, logical, and epistemological subjects in his metaphysical essay Individuals. On balance, metaphysical skepticism must probably be considered as controversial as any of the metaphysical doctrines proposed.

See also Existence; Logic, History of; Meaning; Proper Names and Descriptions; Relations, Internal and External; Substance and Attribute; Universals, A Historical Survey.


For the linguistic aspects consult a standard work, such as Leonard Bloomfield, Language (New York: Holt, 1933), or R. A. Hall Jr., Introductory Linguistics (Philadelphia: Chilton, 1964). Russell's strictures against subject-predicate logic can be found in his discussions of Aristotle and Hegel in his History of Western Philosophy (New York: Simon and Schuster, 1945), and his An Inquiry into Meaning and Truth (New York: Norton, 1940) contains discussions of both logical and epistemological aspects of the question, as well as comments on Wittgenstein. Russell's paper "On Denoting" can be found in Logic and Knowledge (New York: Macmillan, 1956), together with other relevant papers. Frege's views are readily accessible in Translations from the Philosophical Writings of Gottlob Frege, edited by P. T. Geach and Max Black (Oxford: Blackwell, 1952). Wittgenstein's Tractatus Logico-Philosophicus has had a more profound influence with respect to semantics and logical form than any other twentieth-century work. Mill's discussion of connotation and denotation can be found in Book I of his System of Logic.

The chief items by Aristotle are On Interpretation, Categories, the opening paragraph of Prior Analytics, and Book Zeta of the Metaphysics ; by Hegel, The Phenomenology of the Mind, especially the preface; by Leibniz, Monadology ; by Carnap, P. A. Schilpp, ed., The Philosophy of Rudolf Carnap (La Salle, IL: Open Court, 1963), the autobiographical essay and the replies; by Black, Models and Metaphors (Ithaca, NY: Cornell University Press, 1962); by Geach, Reference and Generality (Ithaca, NY: Cornell University Press, 1962).

G. E. M. Anscombe and P. T. Geach, Three Philosophers (Ithaca, NY: Cornell University Press, 1961), contains useful comments on the relevant views of Aristotle and Frege. One of the best more recent discussions of the influence of grammar on metaphysics is Morris Lazerowitz, "Substratum," in Philosophical Analysis, edited by Max Black (Ithaca, NY: Cornell University Press, 1950). For further references, see the articles cited in text and entries on the philosophers mentioned.

Newton Garver (1967)