第一节 选题
语法学家们历来都十分关注本书中的研究对象——主位化评述结构。以Jespersen (1933，2006)为例，他把以下句子结构称为外置结构(extraposition)。
(1) It is a pleasure to teach her to drive.
Quirk等(1985: 1391)认为，这种结构除了外置的－ing小句在非正式场合中不常见外，这种外置结构可以分成以下七种类型:
1) SVC: It is a pleasure to teach her.
2) SVA: It was on the news that income tax is to be lowered.
3) SV: It doesn't matter what you do.
4) SVO: It surprised me to hear him say that.
5) SVOC: It makes her happy to see others enjoying themselves.
6) SVpass: It is said that she slipped arsenic into his tea.
7) SVpassC: It was considered impossible for anyone to escape.
我们把研究对象限定在除了Quirk等所定义的七种类型外，还包括带形容词补语的It seems strange...和It appears reasonable ...两种类型的结构，因为根据Quirk等的看法，这一类的小句具有和前面七种类型相似的外置结构(Quirk et al.，1985: 1392)。
(2)It appears reasonable to claim that a man without the capacity to put himself in another's place could not understand a moral appeal (even if he should happen to be a law－abiding man who accepts commands and prohibitions on external authority)，just as someone incapable of shifting temporal viewpoints could not understand an appeal to his future interests.
(3)It seems strange that I can spend ten times as much on a Fender product and be provided with none of this! When it comes to tradein time，I think we'll be looking at Gibson，Ibanez，Yamaha and the other competitors，excellent product though the Squier Hank Marvin is.但不包括下面的例句(4)和例句(5)这种句子类型，原因在于这种结构没有对应的一致式结构(congruent form)。如例句(* 4)和例句(*5)就不存在。
(4)It seems that the length of time in them answering reflects the fact that all these sort of pollution inspectorates and Health and Safety Executives are understaffed.
(*4) That the length of time in them answering reflects the fact that all these sort of pollution inspectorates and Health and Safety Executives are understaffed seems.
(5)It appears that there are many points at which er we can identify with one another or I have found that I can identify with the church and its social responsibility in this country because of our experience in my country.
(*5) That there are many points at which er we can identify with one another or I have found that I can identify with the church and its social responsibility in this country because of our experience in my country apprars.
尽管对于这一结构中的主语“It”，不同研究者有不同的称谓，如“preparatory it”或“dummy it”(参见Jespersen，1933; Hasselga。rd et al.，1998)，本书采用Quirk等(1985)的术语称其为预指代词it或引词it (anticipatory it)。
围绕这一结构有两个引人注目的问题。
其一，后置的小句的选择问题。现有的文献表明，对后置的小句和非后置小句的选择主要出于修辞性和非修辞性的目的。前一类看法认为，句子的主语越长被后置的概率就越大(Quirk et al.，1985: 1392)。后一种看法认为，在相同的条件下，小句越复杂就越可能被后置(Bloor and Bloor，1995: 167)。Hasselga。rd等(1998)认为，后置的小句存在的原因在于“信息原则”(information principle)，也被称为“句末重心原则”——把句子所传递的信息划分为“新信息”和“已知信息”，而且说/写者倾向于把新信息置于句末，而这些信息通常是信息承载较重的并且较长的成分。
其二，关于这种结构的一致式或非一致式的选择问题，Ward、Birner和Huddleston (2002: 1403)认为是由三个相互作用的因素共同决定的:语境(context)、句子承重(syntactic weight)和可加工性(processability)。而Biber等(2000: 676)则认为是由下面四种语法和语篇的因素决定的:语域(register)、信息结构(imformation structure)、语法复杂性(grammatical complesity)、话题和个人风格(topic and personal style)。
Kaltenb
ck (2004)认为，信息结构、语域和结尾重心原则等是影响说/写者选择这种结构的一致式(conguent form)而不是它对应的非一致式(non－congruent)。他认为一致式在口语和写作中表现出的优势(口语中占90.2%，写作中占87.6%)与英语的轻主语(light subject)的语言习惯有关，根据Given (1995)的标记理论，他得出的结论是:一致式是非标记的，非一致式是有标记的。这和传统上语言学家们认为非外位结构更常见的观点相反。因为非外位结构给人的感觉更像基本的句子结构，语序也更规范。
上述研究是分别从语义、语境、语域、信息结构和句子承载等方面来研究的，我们认为，可以从评价的角度来研究这一结构。根据Martin和White的评价理论(2005)，以及Halliday (1994，2004)、Thompson和Fawcett等(2008)的研究来看，这一结构不但含有丰富的词汇评价手段，而且这一结构本身也有评价意义，值得我们去探究。
Biber等(1999)把这种结构看成是一种表明立场的语法手段(grammatical stance device)，或者是一种立场标记(stance marker)并把它归到表立场的补语小句一类中。他们认为，这种结构所描述的立场有时是显性的［如例句(6)］，有时是隐性的［如例句(7)］，有时无法判断其立场来源到底是说话者还是第三方［如例句(8)］。
(6)It amazes me that they can just stand on the street.
(7)It seems strange that her career has been made up entirely of films
that really haven't been all that good.
(8)It was expected that they would interview him later today.
Halliday把这种结构和事实投射(fact projection)联系起来，并把这种结构称为后置主语(postposed subject)，镶嵌于一个事实从句中(1994: 60，2004: 97)。Thompson认为，这是一种特殊的主位结构，与谓项主位结构(predicted theme)类似，允许说话人把他们的评论(如价值和正当性)作为信息的出发点。由于这种结构可以用来表达评价和显性客观情态，因此他把这一结构称为主位化评述结构(The Thematized Comment Construction) (2008: 152－153)。Fawcett (2003)和黄国文(2003)把这种结构作为强势主位结构中的一种，把它称为评价性强势主位结构(the Evaluative Enhanced Theme Construction)。
本书采用Thompson的术语，把所要研究的对象称为主位化评述结构(The Thematized Comment Construction)。鉴于这种结构明显的评价特点，以下简称“TCC评价结构”。本书将从回顾文献对主位化评述结构的研究入手，分析现有的评价理论对这一结构的解释，并在这一基础之上研究和讨论它的评价功能及其机制。