II. Subject vs. Topic.*

(a) Definite.

According to Chafe (this volume), a definite noun phrase is one for which

"I think you already know and can identify the particular referent I have in mind."
One of the primary characteristics of topics, then, is that they must be definite2 (see Chafe, this volume, for further remarks on definiteness).

According to this characterization of definiteness, proper and generic NPs are also understood as definite. The conditions regarding the speaker's assessment of the hearer's knowledge under which a proper noun can be appropriately used are the same as those under which a definite common noun phrase can be used. A generic noun phrase is definite because its referent is the class of items named by the noun phrase, which the hearer can be assumed to know about if he knows the meaning of that noun phrase.3

A subject, on the other hand, need not be definite. For example, the subjects of 3 and 4 are indefinite:

 
3 A couple of people have arrived.
4 A piece of pie is on the table.
 
(b) Selectional relations.

An important property of the topic is that it need not have a selectional relation with any verb in a sentence; that is, it need not be an argument of a predicative constituent. This property of topic is

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particularly noticeable among the topic-prominent languages since the topic-comment construction in such languages, as we will try to show, represents the basic sentence type. Consider sentences 5, 6, 7, and 8, all of which represent common sentence types in their respective languages. The underlined constituent in each sentence is the topic.

 

The topics in these sentences, 5 "this field," 6 "elephants," 7 "that fire," 8 "those trees," have no selectional relation with the verbs. Similarly, in Japanese, the topic marked by the particle wa, and in Korean, the topic marked by the particle (n)un  need not be selectionally related to the verb of the sentence, as shown in 9 and 10:

 
9 siban-un kakkjo-ga manso (Korean)
now-topic marker school-subject marker many
    "The present time (topic), there are many schools." 
 
10 Gakkoo-wa buku-ga isogasi-kat-ta (Japanese)
school-topic marker I-subject marker busy-past tense
    "School (topic), I was busy."
 
The subject, on the other hand, always has a selectional relation with some predicate in the sentence. It is true that the surface subject of some sentences may not be selectionally related to the main surface verb. For example, classical transformational analyses (e.g., Chomsky 1965; Rosenbaum 1967; Postal 1971; Postal and Ross 1971) recognize the surface subject. "John," in the following sentences to be selectionally unrelated to the main predicates, "be easy" and "appear."

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11 John is easy to please.
12 John appears to be angry.
This fact, however, does not contradict our claim that the subject of a sentence is always selectionally related to some predicate in the sentence. In the surface structure, the subject might not be adjacent to the predicate to which it is selectionally related, and it might even have assumed a new grammatical relationship with a verb to which it is not selectionally related. But the fact remains that a selectional relation must exist between the subject of a sentence and some verb in that sentence4, whereas no such relationship need exist between topic and verb.5
 

(c) Verb determines "Subject" but not "Topic."

A correlate of the fact that a subject is selectionally related to the verb is the fact that, with certain qualifications, it is possible to predict what the subject of any given verb will be.6 Thus, in English, if a verb occurs with an agent as well as other noun phrases, the agent will become the subject unless a "special" construction is resorted to, such as the passive. (This way of stating the fact about subjectivalization is due to Fillmore, 1968:37.) If the verb is intransitive, either the patient or the actor, depending on whether the verb is a stative verb or an action verb, will be the subject. If the verb is causative, the causer will be the subject. These facts represent some of the language-independent generalizations about how the subject is determined by the verb. There is no doubt that not all verbs in a language can be classified with respect to subjectivization on a language-independent basis. For example, in English, the verb "enjoy" will take the experiencer but not the accusative as the subject, whereas the verb "please" will have the accusative noun phrase but not the experiencer as the subject. But the fact remains that given a verb, the subject is predictable.

The topic, on the other hand, is not determined by the verb; topic selection is independent of the verb. Discourse may play a role in the selection of the topic, but within the constraints of the discourse, the speaker still has considerable freedom in choosing a topic noun phrase regardless of what the verb is. This characteristic of the topic is clearly demonstrated by our earlier examples, 5-8, with topic-comment structure.
 

(d) Functional role.

The functional role of the topic is constant across sentences; as Chafe (this volume) suggests:

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"What the topics appear to do is limit the applicability of the main predication to a certain restricted domain. . . . The topic sets a spatial, temporal, or individual framework within which the main predication holds."
Clearly, this function of specifying the domain within which the predication holds is related to the structure of the discourse in which the sentence is found. The topic is the "cencer of attention"; it announces the theme of the discourse. This is why the topic must be definite (see section II(a) above). The functional role of the topic as setting the framework within which the predication holds precludes the possibility of an indefinite topic. A feel for the bizarreness of such a topic can be gained from considering the impossibility of interpreting the following English sentence:  
0
13 *A dog, I gave some food to it yesterday.
one
  Looking at the functional role of the subject, on the other hand, reveals two facts. First, some NPs which can be clearly identified as subjects do not play any semantic role in the sentence at all; that is, in many subject-prominent languages, sentences may occur with "empty" or "dummy" subjects (see section III(c) below). Second, in case the subject NP is not empty, the functional role of the subject can be defined within the confines of a sentence as opposed to a discourse. According to Michael Noonan (personal communication), the subject can be characterized as providing the orientation or the point of view of the action, experience, state, etc., denoted by the verb. This difference in the functional roles between the subject and the topic explains the fact that the subject is always an argument of the verb, while the topic need not be (see section II(b) above). The explanation runs as follows: if we are to view the action, experience, state, etc., denoted by the verb from the point of view of an entity (or orient the description towards that entity), the entity must be involved in the action, experience or state, etc., and must therefore be an argument of the verb. Thus we see that the distinct functions of the topic and the subject turn out to explain the differences between them in definiteness and selectional relations.

(e) Verb-agreement.

It is well known that the verb in many languages shows obligatory agreement with the subject of a sentence. Topic-predicate agreement, however, is very rare, and we know of no language in which it is widespread or

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obligatory. The reason for this is quite straightforward: topics, as we have seen, are much more independent of their comments than are subjects of their verbs. Evidence of this independence can be found in the fact, discussed in section II(a) and II(c), that the topic need not have any selectional relationship to any verb and that the topic is not determined by the verb of the sentence. Given this independence, it is to be expected that a constituent in the comment is not normally marked to agree with some grammatical property of the topic. Morphological agreement, then, where some inherent properties of the subject noun are represented by verbal affixes, is a common kind of surface coding for subjects (see E.L. Keenan, Definition of Subject, this volume).7

(f) Sentence-initial position.

Although the surface coding of the topic may involve sentence position as well as morphological markers, it is worth noting that the surface coding of the topic in all the languages we have examined always involve the sentence-initial position. In Lisu, Japanese, and Korean, the topic is obligatorily codified by morpheme markers. In Lahu, the topic is optionally codified by morpheme markers. But regardless of the morpheme markers, the topic in these languages must remain in sentence-initial position. Subject, on the other hand, is not confined to the sentence-initial position. In Malagasy and Chumash, for example, the subject occurs in sentence-final position, while Arabic and Jacaltec, for example, are VSO. The reason that the topic but not the subject must be in sentence-initial position may be understood in terms of discourse strategies. Since speech involves serialization of the information to be communicated, it makes sense that the topic, which represents the discourse theme, should be introduced first. The subject, being a more sentence-oriented notion, need not receive any priority in the serialization process.

(g) Grammatical processes.

The subject but not the topic plays a prominent role in such processes as reflexivization, passivization, Equi-NP deletion, verb serialization and imperativization (see E.L. Keenan, Definition of Subject, this volume). Thus the reflexive pronoun generally marks a co-referential relation with the subject of the sentence; passivization may be viewed, at least in part, as a process promoting the patient to the subjecthood; in Equi-NP deletion, the deleted constituent in the complement is generally the subject; verb serialization which is found in the Niger-Congo languages and the Sino-Tibetan languages, involves the concatenation of a series of verb phrases with one identical subject; the deleted second person morpheme in an imperative sentence is always the subject. The reason that the topic is

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not involved in such grammatical processes is partially due to the fact that the topic, as we have shown earlier, is syntactically independent of the rest of the sentence. Reflexivization, passivization, Equi-NP deletion, verb serialization etc., are concerned with the internal syntactic structure of sentences. Since the topic is syntactically independent in the sentence, it is not surprising that it does not play a role in the statement of these processes.

To sum up this section on the differences between the subject and the topic, we note that seven criteria have been established. These criteria are not intended to constitute a definition of either notion, but are rather designed to serve as guidelines for distinguishing the topic from the subject. We may single out three basic factors underlying these criteria: discourse strategy, noun-verb relations, and grammatical processes. The subject has a minimal discourse function in contrast with the topic. Hence, the topic but not necessarily the subject is discourse-dependent, serves as the center of attention of the sentence, and must be definite. As for noun-verb relations and grammatical processes, it is the subject rather than the topic that figures prominently. Thus, subject is normally determined by the verb, and is selectionally related to the verb; and the subject often obligatorily controls verb agreement. These properties of the subject are not shared by the topic. In conclusion, the topic is a discourse notion, whereas the subject is to a greater extent a sentence-internal notion. The former can be understood best in terms of the discourse and extra-sentential considerations; the latter in terms of its functions within the sentence structure.
 



*Charles N. Li & Sandra A. Thompson. 1976. "Subject and Topic: A New Typology of Language." In: Charles N. Li (ed.). Subject and Topic. London /New York: Academic Press, pp. 461-66.