【摘 要】主位是信息的起點(diǎn)，提供交際雙方已知的信息，述位則是相對(duì)于起點(diǎn)而言的，表達(dá)出作者要傳遞的新信息。句子的主位或述位之間按照一定的規(guī)律不斷聯(lián)系變換，形成主位推進(jìn)模式，而篇章的連貫正是取決于這種主位推進(jìn)模式。

【關(guān)鍵詞】主位；述位；主位推進(jìn)

1.Theme and Rheme

Theme （T） and rheme （R） were first proposed in 1939 by one of the important founders of Prague School， Vitem Mathesius， a Czechoslovak linguist. In his well-known paper in 1939， he defined the first part of the utterance as theme or the starting point of utterance and the second part as rheme or the core of the utterance. Later， he defined theme as the foundation of the utterance which referred to something that was being spoken about in the sentence， and rheme as the core which referred to what the speaker said about the former. Meanwhile Mathesius proposed that theme was something that could be gathered from the previous context， while rheme expressed something new， something unknown from the previous context. That is to say， according to Mathesius theme always carries known or given information， while rheme always carries new information. Mathesius’ research on theme and rheme exerts a great influence on later linguists， such as M. A. K. Halliday， F. Danes， Firbas J and so on.

2.Thematic Progression （TP） Patterns

According to the research about theme and rheme done by the linguists of the Prague School and others， many linguists， both abroad and at home， have conducted the study of thematic structure from the viewpoint of discourse organization， and later put forward the theory of thematic progression. Considering TP patterns proposed by those linguists， in the experiment I adopted four models， namely， parallel progression pattern， focused progression pattern， simple linear progression pattern， and crossing progression pattern. As Halliday said the thematic organization of the clauses was the most significant factor in the development of the text and by analyzing the thematic structure of a text clause by clause， we can gain insight into its texture and understand how the writer made clear to us the nature of his underlying concerns. it’s true that such analysis of theme types and TP patterns helps us to gain insight into the internal relationships between clauses and how these clauses are structured into a coherent text.

3.The Application of Thematic Theory

1） Reading and writing should be combined closely in the instruction of writing， namely， to improve writing through reading， and to improve writing through writing itself. In this experiment the teacher should introduce the theory briefly first， which may help students understand how themes and TP patterns function in the paragraphs and how the lexical cohesive ties are used in the clauses. Second， explicit explanations should be given to students， if possible， authentic samples in the texts being used. Third， students engage in a range of text analysis tasks in order to apply the concepts they have learnt. At this stage students may try to analyze some texts given by the teacher and then check their answer together with their teacher. Finally， it’s time for students to write， that is to apply the learned knowledge in the practical writing. The teacher arranges different tasks according to different instruction contents. So it’s very clear reading and writing are both inevitable in the instruction. Without appropriate reading， the theory cannot be understood deeply， not to mention the application of the theory， while without enough writing， all the former works are useless.

2） Students’ English level should be taken into consideration during the instruction of thematic theory. Actually， different levels of students vary in degree of sensitivity to the language teaching. Those who are proficient in using English can do better and master this kind of teaching method more easily and more quickly than those who are not good at English. But even for students with lower English level， thematic analysis and thematic theory can show the advantages. Teachers should make different teaching plans in advance for students with different English levels. For example， we have said that crossing pattern is not easy for the students to grasp. But students of high scores are much better at using crossing and focused patterns in the writing， so in the instruction of higher score students these patterns should be paid special attention to， on the contrary， to students of low scores crossing pattern may not be an inevitable part in the teaching. This is just an example to illustrate my viewpoint； of course， the actual teaching is much more complicated.

3） It is a challenge for teachers to teach thematic theory and it is difficult for the students to grasp the essence of the theory， so it’s both necessary and profitable for teachers to enhance their awareness of thematic theory constantly. Without thorough understanding of thematic theory it is impossible to teach. Therefore， in order to teach students well， teachers should have a profound knowledge first. If our teachers for writing class have mastered the theories and can apply them to coherence teaching， they may not only broaden the students’ view on coherence， but more importantly， they may also provide the students with a new perspective to analyze a text. Therefore， students can use their knowledge of thematic theory in not only writing but also reading. Finally， students’ English can be improved as a whole.