【Abstract】Thematic progression （TP） is a key theory in system?functional grammar. It explains the textual function and text coherence by studying theme， rheme and sentence sequences. Through studying the thematic progression of expository writing， it is found that constant theme pattern and simple linear pattern are mostly used in expository writing.

【Key words】thematic progression； expository writing； system?functional grammar

【中圖分類號(hào)】G42 【文獻(xiàn)標(biāo)識(shí)碼】A 【文章編號(hào)】2095-3089（2013）09-0090-01

1.Introduction

Thematic progression （TP） is important for text coherence. The studies have been conducted by scholars abroad and at home. The concept of theme was firstly pointed out by Czech linguistic F. Danes （1974）. He summarized four types of TP patterns， that is， the constant theme pattern， the simple linear pattern， the derived theme pattern and the split rheme pattern （1974）. Bloor and Bloor （1995） i?dentified the similar patterns. Eggins （2004） pointed out three basic patterns， that is， the theme reiteration， the zig?zag theme pattern and the multiple?rheme pattern. The theme reiteration is similar to the constant theme by Danes （1974）. The zig?zag theme pattern is what Danes （1974） categorized as the simple linear pattern. The multiplevrheme pattern is the same to the split rheme pattern by Danes （1974）. Domestically， scholars have also conducted studies on TP patterns， such as Hu （1994）. Hu has identified four patterns. They are the constant theme pattern， the constant rheme pattern， the simple linear pattern and the exchange pattern.

The text is an expository writing， which introduces folklore in the world. This essay will analyze the writing with the combination of Bloor and Bloor’s hypothesis （1995） and Hu’s （1994） together. Apart from overlapping patterns， six patterns are concerned. They are the constant theme pattern， the simple linear pattern， the derived theme pattern， the split rheme pattern， the constant rheme pattern and the exchange pattern.

2.Relations between Topic Clauses and the Opening Clause

In terms of lexical sense relation， the themes of topic sentences are hyponyms of the theme of the opening clause. The hyponymy relation between them indicates that their thematic progression pattern is the derived theme pattern. The derived theme pattern of the topic sentences and the opening sentence makes all the paragraphs coherent.

T1 →R1

↓

T4 （=T1）→R4

↓

T14 （=T1）→ R14

↓

T21 （=T1）→ R21

↓

T27 （=T21）→ R27

↓

T33 （=T1）→ R33

↓

T37 （=T33）→ R37

Basically speaking， themes of topic sentences are derived from the theme of the opening sentence. Specifically speaking， except for T27 and T37， all the themes of topic sentences are directly derived from the theme of the opening sentence. T27 is derived from T21， and T37 is derived from T33. The derived theme pattern of the topic sentences and the opening sentence makes all the paragraphs coherent.

3.The Thematic Progression Pattern on the Whole

This analysis combines Bloor and Bloor’s TP pattern （1995） and Hu’s TP pattern （1994）. Apart from overlapping patterns， there are six TP patterns， that is， the constant theme pattern， the simple linear pattern， the derived theme pattern， the split rheme pattern， the constant rheme pattern and the exchange pattern. In this passage， five TP patterns can be found. They are the constant theme pattern， the simple linear pattern， the derived theme pattern， the constant rheme pattern and the exchange pattern. Their frequencies and occurrence rates show below.

Frequencies and rates of each TP pattern

It can be seen from the above table that the mostly occurred pattern is the constant theme pattern， which takes up 45%. The second one is the simple linear pattern， which takes up 30%. The two patterns altogether occupies 75%， hence the basic TP patterns that make the text coherent are the constant theme pattern and the simple linear pattern.

The result of using these two patterns most is related to the fact that this passage is an expository writing. It presents much information. These two patterns are helpful to make the whole passage orderly， clearly， and coherently.

The derived linear pattern between the theme of topic clauses and that of the opening clause makes the structure of passage clearly and coherently. The author of this passage firstly told readers what this passage is about. It is about folklore. Then the author introduced the subordinate of folklore one by one.

Besides， when the passage explains or presents certain things， it tends to use the constant theme pattern. Hence clauses are closely related to one another and information is clearly present. When the passage introduces new information， it tends to use the simple linear theme patterns. It makes the neighbor clauses related to each other. So the constant theme pattern and the simple linear pattern are basic patterns that make the text globally coherent.

Reference：

[1]Bloor， T Bloor， M. （1995）. The Functional Analysis of English： A Hallidayan Approach. London： Arnold.

[2]Danes， F. （1974） Fuctional Sentence Perspective and the Organization of the Text. Papers in Functional Sentence Perspective. Prague： Academic.

[3]Eggins， S. （2004）. An Introduction to Systemic Functional Linguistics. New York： Continuum.

[4]Thompson， G.（2008）. Introducing Functional Grammar. Beijing： Foreign Language Teaching and Research Press Hodder Arnold.

[5]胡壯麟. 語篇的銜接與連貫. 上海： 上海外語教育出版社， 1994.