情事變更原則的變遷與理論基礎

The Evolution of Principle of Change of Circumstances and Its Theoretical Foundation

於未預期事件發生時，債務人之義務可能發生給付不能或給付困難，債權人之契約目的亦可能喪失。羅馬法自古以來討論給付不能法則，作為契約嚴守原則的例外。就給付困難之情形，羅馬法無情事變更原則，教會法雖承認之，但19世紀法學逐漸衰微，各國法制多數繼受羅馬法的給付不能法則，但無情事變更原則。在第一次世界大戰後，德國面臨巨大經濟變遷導致貨幣急速貶值，逐漸發展出情事變更原則。法國民法200年來不承認情事變更原則，直到2016年新民法始承認之。英國法以契約挫敗法則，涵蓋給付不能、給付困難及給付目的障礙之案件，美國法基本上承襲英國法，而稍有不同。本文論述情事變更原則於歐陸法及英美法的法制變遷，自其發展的學說與實務見解，探尋情事變更原則的立論基礎。

When supervening events occur, a debtor’s performance may become impossible or more onerous than expected, and a creditor’s contractual purpose may be frustrated. The doctrine of impossibility has been adopted to exclude the strict application of pacta sunt servanda since Roman law. In cases of hardship, the clausula rebus sic stantibus did not appear in Roman law but was recognized under the canon law. However, the clausula rebus sic stantibus fell into decline in 19th century jurisprudence, when most jurisdictions accepted the doctrine of impossibility without adopting the clausula. In the aftermath of World War I, Germany experienced severe economic changes, resulting in a rapid decline in currency values. As a result, clausula rebus sic stantibus was gradually revived. French law did not recognize clausula rebus sic stantibus for two centuries until its recognition in 2016. The doctrine of frustration in English law covers impossibility, hardship, and frustration of purpose. American law adopts the English doctrine with minor revisions. This paper discusses the development of clausula rebus sic stantibus in Continental and Common law and explores its fundamental theories, drawing on historical legal theories and court decisions.