systematicity， unidirectionality and partiality.It may fulfill one or more than one role among the following：structuring the target do-main concept， providing options to instantiate the target domain， providing bases for the reasoning and evaluating about the target do-main.It is noted that a conventional vehicle as the source domain can cognize a target domain conveniently and effortlessly.
Metaphorical mapping is closely linked with the discourse it con-structs.A discourse in this book is regarded as a stretch of relatively formal language either in the written form or the spoken form to per-form a certain function among description， exposition， argumentation and narration in unity of cognition， linguistic form and context.A discourse can be a whole passage or part of it， even a huge book.
In line with this definition of discourse， a metaphorical discourse is defined as a stretch of relatively formal language either in the writ-ten form or the spoken form governed by the influence of a single metaphor or multiple metaphors， either implicit or explicit， that makes a relatively independent whole to carry out a certain function among description， exposition， argumentation and narration， with some effects in unity of cognition， linguistic form and context.
A metaphorical discourse has the following quali f ying factors：Firstly， metaphor in the discourse is restricted to its narrow senseie， based on similarity or similarities created by the metaphorical mapping， Secondly， the discourse is either in the written form or the spoken form.This is to extend to oral metaphors that occur in rela-tively formal speeches.Thirdly， it stops where the influence of a sin-gle metaphor or multiple metaphors can exert.
……
展开
