本文探討了先前Li & Thompson (1977)，Yen (1986)以及Feng (1993)有關漢語系詞「是」的發展看法，作者認為Li & Thompson (1977)的主題機制(topic mechanism)，Yen (1986)的類比改變(analogical change)以及Feng (1993)的語音停頓(phonological pause)觀點雖有意義，但皆未能對漢語系詞的發展提供令人滿意的解釋。本文採用了Katz’s (1996)的認知概念，認為代詞和系詞在時間與空間上之存在的認知關聯使兩者產生了關係，而古文獻中指示代詞的「是」和動詞的「是」出現在同一個句法環境則誘發了指示代詞的「是」發展成為後來的系詞。

This paper discusses the proposals of Li and Thompson (1977), Yen (1986), and Feng (1993) in relation to the development of the Chinese copula and argues that Li and Thompson's suggestion of a topic mechanism, Yen's analogical change, and Feng's phonological pause are unsatisfactory in explaining the development of the copula. It is suggested that Katz's (1996) cognitive concept of existence in time and space between pronouns and copulas is what relates the demonstrative pronoun shi to a copula, while the verbal form shi occurring in the same syntactic context as the demonstrative pronoun shi is what triggers this demonstrative pronoun to turn into a copula.