Abstract: With two predicates and one argument，the English tough-construction has its own unique syntactic and semantic properties．Syntacticians，under the framework of principles & parameters，have put forward several proposals for its derivations：argument movement，non-argument movement，side-ward movement，and copy-raising，etc．However，all these proposals are either in conflict with Thetacriterion and/or Case-filter，or in the confusion of the argument and non-argument movements，thus being unable to provide an adequate account for its derivational mechanism．The present article proposes that the core question that should be dealt with under the framework of Minimalist Program is to explore the motivations for the theta-role sharing by both the subject and the null operator and to crystalize how such sharing is materialized．

Keywords: Principles & Parameters; tough-construction; argument movement / non-argument movement; sideward movement; copy-raising

摘要： 具有两个谓词和一个论元的英语tough结构有其自身独具的句法语义属性。句法学家们在原则和参数理论框架下为该结构的推导生成提出了各种分析方案：论元移位、非论元移位、侧向移位以及拷贝—提升等分析法。但这些方案要么有违题元准则和/或格位过滤原则，要么混同了论元移位和非论元移位，因此都不能充分解释该结构的生成机制。本论文认为，未来基于最简方案的相关研究应该解决的核心问题是：该结构的主句主语和不定式句中的空算子为何以及如何共享一个题元角色。

关键词: 原则和参数, tough结构, 论元/非论元移位, 侧向移位, 拷贝提升