Coherence is a term of text linguistics used to refer to sense relations between single units (sentences or propositions) of a text. Due to these relations, the text appears to be logically and semantically consistent for the reader-hearer. Text analysis focussing on coherence is primarily concerned with the construction and configuration of sense in the text i.e. how its single constituents are connected so that the text becomes meaningful for the addressee rather than being a random sequence of unrelated sentences and clauses.
Coherence vs. Cohesion
Text linguistics is concerned with the distinction between the terms 'cohesion' and 'coherence' (cf. Halliday 1994: 308-309; see also de Beaugrande and Dressler 1992: 3-7). Halliday (1994: 308-309) distinguishes between coherence and cohesion in terms of internal and external relations of a clause. Coherence is "the internal [resource] for structuring the clause as a message", including the notions of 'theme' and 'information', and cohesion refers to the external relationship between clauses and clause complexes, which are independent of grammatical structure.
Brinker (2005: 21-22) points out that the textual structure can be analysed both on a grammatical and on a thematic level, i.e. with respect to the syntactic-semantic relations between sentences (cohesion) and the logic-semantic relations established between propositions making up the thematic structure.
The question of the functional connection between cohesion and coherence has raised much debate, most of the controversy discussing whether cohesion is a sufficient criterion for textual coherence or not. In several cases coherence has been regarded as a subject to, or pre-conditioned by, cohesion (Halliday 1994: 339). Hasan & Halliday (1976: 9) even maintained that cohesion is "the ONLY source of texture". These views have been challenged vehemently by others, however (see Brinker 2005: 41; Hellmann 1995: 193; Brown & Yule 1993: 227).
As a rule of thumb, a text can be coherent without being cohesive, and vice versa. Thus, the reader can still perceive coherence in a sequence of clauses and sentences even if the semantic and syntactic ties connecting them are missing. On the other hand, even if a text shows a strong degree of cohesion, with its constituents being interlinked by many cohesive ties, it does not need to be coherent. Consider, for instance, the following example:
"Yesterday I met an old friend in London. In London, there are numerous public libraries. These libraries were visited by boys and girls. The boys are handsome, and they often go to public swimming pools. These swimming pools were closed for several weeks last year. A week has seven days. Seven days ago I visited my grandparents in San José …" (example based on Brinker 2005: 41, slightly modified)
Although the above sentences are interlinked by many cohesive ties, the text reads a bit awkward owing to its lack of coherence. This lack arises because an overall theme underlying the whole structure is missing (see below: theme-rheme structure). Compare, in contrast, the next set of examples:
- It was cold in the room. Someone had opened a window.
- There had been an accident. Two cars had crashed. Two cats died, but there were no human casualties. (example from Brinker 2005: 42; slightly modified)
- John took a train from Paris to Istanbul. He likes spinach. (Kehler 2002: 2)
Sentence (1) contains a slight vestige of cohesion (as exophoric reference).In (2), the coherence of the single sentences is even more. There are no cohesive ties explaining the three sentences as concurrent sense-related events specifying and explaining each other. Although the anaphoric reference pronoun in (3) is a cohesive link, it does not help the reader establish any logical and semantic relation between John traveling from Paris to Istanbul and having a preference for spinach.
Kehler suggests that any reader-hearer draws logical conclusions to find scenarios in which seemingly unrelated sentences become coherent. Thus, it is logical reasoning faculty that allows them to infer the logical relations between propositions from the common theme “the accident and its consequences” in a sentence such as (3).
Establishing coherence in a text is, therefore, a complex cognitive achievement which involves far more than mere text-inherent factors (and, therefore, cohesion), as show by Brown & Yule (1993: 223-270). Each text is a complex message system enabling communication between producer and recipient. The latter always attempts to interpret the intended meaning by making inferences; for the interpretation of the text, however, he or she resorts to both textual (co-text) and extra-textual devices, such as context and background knowledge.
Theme and Rheme
Linguists of the Prague school argued that a sentence can be structured into two parts: a theme and a rheme. According to Vilém Mathesius, theme is the point of departure of a proposition telling what a sentence is about, and rheme an elaboration of the theme (Brinker 2005: 49). The theme-rheme terminology was refined by František Daneš in the 1970s who defined text as a concatenation of propositions in a specific situation and context. He argued that each sentence consists of a theme and a rheme:
“In fast jeder Aussage unterscheidet man das, worüber etwas mitgeteilt wird (DAS THEMA) und das, was darüber mitgeteilt wird (DAS RHEMA, die Aussage im eigenen, engeren Sinne)” (Daneš 1970: 72-73)
Daneš further elaborates that text is a connection of themes which establish a thematic structure. Thus, each sentence might be described as a message system which consists of a theme combined with a rheme (Halliday 1994: 37). As a rule of thumb, the theme is always the left-most constituent in a sentence. Consider the following examples:
|A rough gale||swept over the sea.|
|The Queen||was greeted by people all over the country.|
|The milk can||which had been knocked over in the garden.|
However, terms theme and rheme are sometimes used interchangeably and synonymously with topic and comment (among others by F. Daneš and Brown & Yule: 125pp.) whereas others make a clear-cut distinction between theme-rheme and topic-comment. Halliday(1994: 38) argues that topic is rather a specific kind of theme and more a matter of information structure than of coherence. This article, distinguishes between theme, rheme, and thematic structure. Moreover, Halliday shows that the theme is not always a nominal group but can also be an adverbial group or prepositional phrase.
F. Daneš distinguishes between different patterns of thematic progression depending on whether a theme remains constant, is split up, or changed from one sentence to the next (Daneš 1970: 74-78). These are the five most frequent types of thematic progression:
- simple linear progression, the rheme of the first sentence becomes the theme of a second sentence:
"Peter (T1) recently went to see the Olympic Games in Vancouver (R1). This town (R1=T2) had been named after Captain George Vancouver (R2). The Captain (R2=T3) had spent only one day in the town to meet the Spaniards (R3) ..."
- constant theme, the theme remains constant in the sequence of sentences; only the rheme is changed:
"The throstle (T1) was singing all night (R1). It (T1) was living in a tall tree (R2). It (T1) had a hard time defending its eggs against birds of prey (R3)"
- derived themes, single themes have been derived from a 'hypertheme' (which is 'the geographical data of Romania' in the following example):
"Romania (T1) is situated in Southeastern Europe, on the Lower Danube, bordering on the Black Sea (R1). Its surface area (T2) amounts to 92.043 square miles (R2). Its estimated population (T3) is 22.215.421 inhabitants (R3) ..." (example based on Daneš 1970: 76)
- split rheme, the rheme of a sentence is split into different themes; one double theme is the point of departure for two (or more) independent partial progressions, with one progression being developed after the other:
"At the entrance of a house (T1) two men are waiting (R = R1'+R1). One of them (T2' = R1') is smoking (R2'); the other one (T2 = R1) is drinking (R2) ..."
- thematic lapse, one link of the thematic chain is missing; it might be easily supplemented from the context:
"Peter (T1) entered the dark room (R1). It (T2 = R1) was furnished with costly furniture (R2). The carpets (T4) were of bright colours (R4)."
In the above example there is a lapse from furniture to carpets without interrupting the coherence of the sentences. The theme carpets can be inferred from room although the information that the carpets are a part of the furniture is not provided (Brinker 2005: 51). Those types of thematic progression rarely appear independently from each other but tend to be combined in most cases. Furthermore, as Daneš (1970: 78) emphasizes, there are many exceptions, special cases and deviations.
Given that a text, a paragraph of a text, or even only two sentences or clauses have a common theme (such as 'the geographical facts about Romania' in the example given by Daneš above) there must be some common denominator that identifies a sequence of propositions as pertaining to the same theme.
The sentences of a text are rather interlinked by what Kehler (2002: 3), Hobbs (1985: 2) and Sander et al. (1992: 1pp.) call various “coherence relations.” These sense relations, which are also called "propositional relations" by Mann & Thompson (1986: 58pp.), are encoded in the text and identified by the reader who tries to make sense of the text and its constituents. They are simply put, "types of reasons why speakers or writers have added this particular sentence" (Meyer et al. 2005: 151). Coherence relations are sometimes called 'types of thematic development'.
What is proposed here is a classification of theme relations blending categories used by Brinker (2005: 65-87), Meyer et al. (2005: 151-153), and Kehler (2002: 15-23). They are, however, only the most important types, and it should be noted that there are more, as, for example, pointed out by Mann & Thompson (1986: 60-67).
"Dick Gephardt organized rallies for Gore, and Tom Daschle distributed pamphlets for him."(Kehler 2002: 16)
- description, a theme is split up into its components; it is specified and situated in space and time. The descriptive theme development either refers to a unique historical event (i.e. in news and reports), a process that is generalized or repeated (i.e. found in recipes, encyclopaedia entries, manuals etc.), or the description of either a living creature or an object (as found, for instance, in dictionary articles)
- narration, especially found in recounting of everyday situations, in newspaper articles, in narratives etc.; the elements in a narrative are usually ordered according to the linear order of the events described (compare: temporal relation)
"The U.S. Geological Survey says eight Haitian cities and towns - including this capital of 3 million - suffered "violent" to "extreme" shaking in last month's 7-magnitude quake (...). In Chile, no urban area suffered more than "severe" shaking - the third most serious level - Saturday in its 8.8-magnitude disaster, by USGS measure." (http://news.yahoo.com/s/ap/20100228/ap_on_re_la_am_ca/cb_tale_of_two_quakes, 4 March 2010, 2:45 p.m.; slightly modified)
"The Atlantic bluefin tuna is considered a delicacy from Osaka to Omaha. In Tokyo's venerable Tsukiji fish market, a single giant blue tuna can fetch up to $100,000 in auction." (http://www.time.com/time/health/article/0,8599,1969589,00.html#ixzz0hDLxeB5k
- temporal relation, a temporal relation can be marked both explicitly (i.e. by cohesive ties) and implicitly (inferred by the reader)
"The Caterpillar and Alice looked at each other for some time in silence: at last the Caterpillar took the hookah out of its mouth, and addressed her in a languid, sleepy voice. 'Who are you?' said the Caterpillar [...]. "(Carroll, Lewis (1993). Alice's Adventures in Wonderland. London: Wordsworth. 49)
"George is a politician. Therefore, he's dishonest. (result)
George is dishonest. He's a politician. (explanation) (both: Kehler 2002: 20-21)"
- argumentation, the speaker or writer introduces an argument and backs it up by supporting facts or other pieces of evidence:
"The introduction of genetically modified (GM) food and crops has been a disaster. The science of taking genes from one species and inserting them into another poses a serious threat to biodiversity and our own health. In addition, the real reason for their development has not been to end world hunger but to increase the stranglehold multinational biotech companies already have on food production[...]"(http://www.greenpeace.org.uk/gm, 4 March 2010, 2:49 p.m.)
References and Recommended Reading
- Brinker, Klaus (2005). Linguistische Textanalyse. Eine Einführung in Grundbegriffe und Methoden. 6th ed. Berlin: Erich Schmidt Verlag.
- Brown, Gillian & George Yule (1993). Discourse Analysis. Cambridge: Cambridge University Press.
- Bublitz, Wolfram (2000). “Cohesion and Coherence.” In: Verschueren, Jef et al., eds. Handbook of Pragmatics. 1998 Installment. Amsterdam: Benjamins. 1-15.
- Daneš, František (1970). “Zur linguistischen Analyse der Textstruktur.” Folia Linguistica 4: 72-78.
- De Beaugrande, Robert & Wolfgang Dressler (1992). Introduction to Text Linguistics. London & New York: Longman.
- Halliday, Michael (1994). An Introduction to Functional Grammar. 2nd ed. London et al.: Edward Arnold.
- Halliday, Michael & Ruqaiya Hasan (1976). Cohesion in English. London & New York: Longman.
- Hellmann, Christina (1995). “The Notion of Coherence in Discourse.” In: Rickheit, Gert & Christopher Habel, eds.
- Focus and Coherence in Discourse Processing. Research in Text Theory. Vol. 22. Ed. János S. Petöfi. Berlin & New York: de Gruyter. 190-202.
- Hobbs, Jerry R. (1979). “Coherence and Coreference.” Cognitive Science 3: 67-90.
- --- (1985). “On the Coherence and Structure of Discourse” (Report No. CSLI-85-37). Stanford, Calif.: Center for the Study of Language and Information. 1-35.
- Hobbs, Jerry R. & Michael Agar (1985). “The Coherence of Incoherent Discourse.” Journal of Language and Social Psychology 4: 213-232.
- Kehler, Andrew (2002). Coherence, Reference, and the Theory of Grammar. Stanford, Calif.: CSLI Publishers.
- Mann, William C. & Sandra A. Thompson (1986). “Relational Propositions in Discourse.” Discourse Processes 9: 57-90.
- Meyer, Paul Georg et al. (2005). Synchronic English Linguistics: An Introduction. 3rd ed. Tübingen: Narr Verlag.
- Sanders, Ted J. M. et al. (1992). “Toward a Taxonomy of Coherence Relations.” Discourse Processes 15: 1-35.
- Sanders, Ted J. M. & H. Pander Maat (2006). “Cohesion and Coherence: Linguistic Approaches.” In: Brown, Keith, ed. Encyclopedia of Language and Linguistics. 2nd ed. Vol. 2. Amsterdam et al.: Elsevier. 591-595.
- Van Dijk, Teun A. (1980). Textwissenschaft. Eine interdisziplinäre Einführung. Tübingen: Niemeyer.