受到越來越多新興民主國家制訂半總統制憲法的影響，對於半總統制的相關研究也越來越受到重視。依照學界對半總統制的定義，威瑪共和與芬蘭都在 1919 年設計出符合半總統制內涵的憲法，可說是當代最早的兩個半總統制的個案。這兩個國家的憲政運作卻有完全相反的結果:威瑪在 1933 年崩潰，而芬蘭先是渡過經濟危機，更在 80 年代逐漸往議會制轉型。本文擬就制度與非制度因素的互動，討論這兩個個案運作的迥異結果。本文將從憲法理論做比較的出發點，分析兩種不同理論基礎的半總統制憲法，並討論這兩種半總統制憲法在危機社會的運作情況。在威瑪是民主崩潰，而芬蘭則是 延續，並且在外部危機消退後逐步向議會制轉型。制度具有的根本差異，加上外在環境的因素，是造成兩個半總統制國家一個崩潰，一個穩定轉型的因素。許多新興民主國家設計半總統制憲法之後，開始追求制度化與民主穩定的目標，這兩個國家的歷史經驗當可以提供一些比較的經驗。

As democratization spread in Eastern and Central Europe over the last two decades, Semi-Presidentialism has become a concept with more attention paid when discussing constitutional issues. By definition, the Weimar Republic and Finland were two of the initial experiments of semi- presidentialism. However, the constitutional practices in the Weimar Republic and Finland are worlds apart. Both semi-presidential, the Weimar Republic had broken down but Finland became a quasi-parliamentary democracy. This paper intends on discussing the differential essences of the semi-presidential constitutions. We will also compare the discrepancy between constitutional essence and practice of these two semi-presidential regimes. The different experiences of the Weimar Republic and Finland can inspire new Semi-Presidential democracies.