文頭における「でなければ」の構文分析

Abstract

The phrase “denakereba” which appears at the beginning of a sentence is structurally characterized by always being accompanied by “de” without an accompanying preceding word. It is mainly used as the first clause in idiomatic expressions such as “nakerebanaranai”(must do), “nakerebaikenai” (must not do), where the second clause “naranai” or “ikenai” is omitted, and functions as a predicate expressing obligation. However, when the preceding word is omitted and “de nakereba” primarily works at the beginning of a sentence, it is not necessarily an expression of obligation. In this paper, we mainly examined the non-conditional usage of “denakereba” that has a conditional usage. In particular, we analyzed the syntax of “denakereba” at the beginning of a sentence and examined what syntactic features it has when it does not take a causal relationship structure. It can be divided into two patterns: when the preceding predicate of “denakereba” takes a modality form and when “denakereba” expresses “presenting choices” such as “A or B.” In both cases, “denakereba” has an independent form and autonomy, which is considered as its unique usage and expands its function to that of a conjunction. This phenomenon can also be seen as an example of the “grammaticalization” of a conditional form to a non-conditional usage.