錯誤 개념의 定立을 위한 小考

§ 109 of Korean Civil Code stipulates that a party of a contract may avoid the contract in case of mistake, when additional requirements are satisfied. Original purpose of § 109 is to make a party under those requirements avoid his/her bondage from contract when the contract was based on his/her misbelief about facts existing at the time of contract closing. In other words, § 109 has not been set up for cases of later change of circumstance, but set up for cases of original defects in declaration of his/her will in the contract. Theories and precedents in Korea, however, have not clarified the time factor in the concept of “mistake” in § 109. Some scholars and precedents have applied § 109 for cases of later non-fulfillment of future expectations. In contrast, each provisions on mistake at “Principles of European Contract Law”, “UNIDROIT Principles of International Commercial Contracts”, and Second Restatement of US clearly prescribe that mistake provisions could be applied only for mistakes existing when the contract was concluded. Majority of German scholars agree as well that mistake provision of BGB applies only for existing facts, while the provision of BGB does not clearly stipulates it. The contract law, in principle, does not mind change of circumstances after closing of contract. Pacta sunt servanda. The risk from the change is up to each parties, and the law convenes only at the time of extreme injustice, with the concept of good faith. Such concepts as impracticability principle, theory of base of act belong to the area of good faith’(§ 2) principle. Non-fulfillment of future expectation and mistake of pre-existing facts should be clearly discerned so that we should not mix up requirements of non-performance and mistake in reviewing cases.