Before discussing the relationship between text cohesion and voice, we will define the terms “text” and “texture.” A text, according to Halliday (2004), refers to a written product, often treated as a semantic rather than grammatical unit. Therefore, it can be stretched to a super-sentence level, related to more than one clause or even paragraph. We can regard a text as a semantic unit which is “related to a clause or sentence not by size but by realization” (Halliday & Hasan, 1976, pp.1-2). De Beaugrands and Dressler (1981) claimed that a text must accomplish the communicative purpose and, thus, can be defined as a “communicative occurrence”
(p.3). In other words, a text is formed only when the communicative purpose is achieved, which means the reader’s interpretation of a text identical with the writer’s intentions in the text. Thus, we can conclude that a text is a unified stretch of meaning that develops communication between the writer and the reader.
“Texture,” as indicated by Halliday and Hasan (1976), is an indispensable feature that makes a clause or paragraph a text (p.2). Texture in English is made up of two components (Halliday, 1977): (1) “cohesive relations,” (Halliday & Hasan, p.2,) including “referential, substitutive-elliptical, conjunctive and lexical,” and (2) Theme system and information system. The four elements in cohesive relations function as
“cohesive ties” to connect individual clause into a semantically cohesive entity. With cohesive relations, the presupposed can be easily decoded by the presupposing and the coordination of these two helps the text flow. The following example illustrates the idea (Saslow & Mongillo, 1985, p.33):
[2.33] Robots, already taking over human tasks in the automotive field, are beginning to be seen, although to a lesser degree, in other industries as well.
There they build electric motors, small appliances, typewriters, pocket
calculators, and even watches.
In [2.33], readers can interpret the word “they” and “there” in the second sentence as references to “robots” and “in other industries” in the first sentence. The interpretation is based on the reason that the presupposing (robots and in other industries) provides the presupposed (they and there) a source for reference. In other words, the passage cannot have texture without the cohesive ties between “robots”
and “they” or “in other industries” and “there.” Therefore, we can say that the presupposing and the presupposed have interdependent relationship to establish a cohesive relation. It can also be generalized that, in [2.33], cohesion is derived from
“grammatical dependencies” (De Beaugrands & Dressler, 1981, p.3) because of the identical references of “they” and “robots” or “there” and “in other industries.” Then, cohesion can be best viewed as a principal feature responsible for the semantic interrelationship between one item and another and for the continuity of meaning.
From the functional perspective, cohesion can be regarded as the connection of components in surface structure that enhances the communication between readers and writers.
On the other hand, cohesion is also claimed to function as a device to reduce redundancy in text (Stoddard, 1991). As shown in [2.33], pronoun “they” and adverb
“there” are used in order to avoid the repetition of “robots” and “in other industries.”
Besides pronouns and adverbs, “epithets with definite articles and displaced or deleted agents” (Stoddard, p.103) are also the usual ways employed. Stoddard exemplified the idea particularly by passive construction. He contended that the application of passive voice depends on whether writers intend to delete agent to avoid text redundancy. For example,
[2.34] One of these relatively new hybrid breeding methods is tissue culture, in which cells are taken from a plant and then grown in vitro in a nutrient solution. In one research project, plant geneticists are striving to develop crops (such as oats) that can grow and reproduce in saline soils, which are a major problem for many farmers. (Saslow & Mongillo, 1985, p.159)
In [2.34], “plant geneticists” are deleted in the sentence “in which cells are taken from a plant and then grown in vitro in a nutrient solution” to reduce text redundancy because it is implied in the context.
Among the four elements that compose cohesive relations, Halliday and Hasan (1976) suggested that operator ellipsis is the one directly related to voice choice.
Operator ellipsis is the ellipsis which functions from the left of the sentence. In other words, what is omitted is only the operator or what we normally called “subject” of a clause. Thus, the subject must be presupposed if operator ellipsis occurs as [2.35]
(Saslow & Mongillo, 1986, p.107) suggests:
[2.35] The satellite will have gigantic solar cell panel wings that will stretch several kilometers. The solar panels will convert the sun’s rays into electrical energy, which will then be transformed into microwaves and beamed to an earth-based antenna.
The clause “which will then be transformed into microwaves and beamed to an earth-based antenna” in [2.35] is perceived as acceptable because the subject of the clause “beamed to an earth-based antenna” is the same as that of the preceding one and omitted. It, therefore, forms a semantically continuous clause. In fact, since subject is always omitted in operator ellipsis, “voice selection must be presupposed if the presupposing group is elliptical” (Halliday & Hasan, 1976, p. 183). Thus, in [2.35]
because “which will then be” is omitted, voice used in the clause “beamed to an
earth-based antenna” must be identical with the preceding clause “which will then be transformed into microwaves,” that is, passive voice in this case.
The second component that forms texture is theme and information systems. As indicated in the previous section, since theme is considered as the point of departure in a clause and the element directing the whole clause, the application of the same or interrelated themes in a paragraph appears essential in constructing a cohesive text. In information system, the word order of a given clause is often influenced by the given-to-new principle and also dependent on which element is considered as shared knowledge (given) or which element’s “meaning is non-recoverable in the context”
(Halliday, 1977, p.32) (new). In the previous section, we have suggested: (1) from the perspective of theme system, voice selection in research articles is one of the devices to thematize the most appropriate constituent to the initial position; (2) from the perspective of information system, voice may change the focus in a clause by assigning given and new information to either the subject or the object of the clause in order to promote the flow of information. Therefore, voice choice seems to play a critical role in discourse organization since voice selection in one clause might be dependent on the preceding one(s) and affect what comes after as well. The appropriate choice between active and passive voice functions to tie the whole text together by building a solid relationship between the previous and the ensuing clauses.