Polysemous Simple Past Tense: A Cognitive Study

English tense system has long been a focus of linguists and grammarians. In order to conduct research in tense system, the simple past tense is chosen as the initial point in tense system. Simple past tense is viewed as a grammatical category which is deictic to past time in traditional study. Although subsequent"remoteness"views free it from grammatical category, they fail to explore the cognitive mechanisms beneath the grammatical unit.Simple past tense not only refers to event past or state past, it can also be used to indicate habitual past, counterfactual past, narrativity, indirect speech and pragmatic softening. Grammar does not mean prescribed rules, but they are symbolic units with meaning from cognitive grammar perspective. Therefore, simple past tense is taken as a grammatical unit with polysemous meaning. So several questions arise from the polysemous phenomena: why is it used in pragmatic softening? Why is it used in fictional narratives? What are the cognitive mechanisms which motivate the meaning extension?The thesis aims to explore the cognitive mechanisms behind the grammatical structure through investigating the six different uses in the polysemous category in details within theoretical framework of metonymy, metaphor, and mental space theory. The basic hypothesis resides in that polysemization in simple past tense is a cognitive process in which different uses are metaphorically or metonymically related and new mental spaces are built in non-typical past tense uses.Cognitive linguistics hypothesizes that there are close relation between language and cognition, and grammatical category is largely in accordance with human cognition rules. The research in the thesis shows that there are mainly two mechanisms within meaning extension: metonymy and metaphor. Metonymy enables mapping within time domain in meaning extension. Once meanings extend beyond time domain, metaphor comes into play. Therefore, metonymy and metaphor, which are cognitive mechanisms in human conceptual thinking, also play an important role in grammatical structure. And meaning extension process in polysemous category is essentially configuration of new mental spaces. Different uses of past tense arise because different spaces are built through shift of V-POINT and FOCUS.The involved cognitive theories in the thesis are not unrelated at all. Both metaphor and metonymy are mapping from one to the other. Metonymy is mapping within one domain and therefore, it often serves as the base and starting point of metaphor. Mental space theory is an important theory about meaning, which plays a crucial role in meaning construction in the meaning extension process. Meaning extension process in past tense is essentially configuration of different mental spaces. Metonymy and metaphor are basic cognitive mechanisms under meaning extension, while mental space configuration is the means by which meaning extension is realized.Thus a better understanding of the past tense can be achieved theoretically by investigating cognitive mechanisms in different uses. In practice, it can be helpful in English learning since tense system is difficult for both elementary and advanced learners. Cognitive linguistic offers a new perspective to perceive tense.