为什么不能说“都以前……”

This paper mainly explains why the adverb of scope "dōu" can not be followed by the adverb of time "yǐqián" when they occur in one and same sentence. Generally speaking, the adverb of scope "dōu" always modifies the constituent that comes before it. As an adverb of time, "yǐqián" indicates either a point or a period of time. When both are used as adverbial in the same sentence, "yǐqián" denotes exclusively the latter while "dōu" is semantically related to "yǐqián" as well as to the subject. In this case, "yǐqián" must precede "dōu" which is semantically a front pointing modifier.