日本法上法律行為無效之研究―以錯誤及意思能力欠缺為例―

Abstract

法律行為若為無效，傳統學說向來認為係指法律行為在法律上「自始、當然、確定不生效力」，並且以「絕對」為原則，任何人均得主張該無效，並且得對於任何主張該無效而言。此種觀點應係早期研究者參考日本文獻而成，並為後繼的學者持續傳承，早已行之有年，可謂成為通說。 我國傳統通說又將無效之法律行為分成「絕對無效」與「相對無效」，並舉出民法第87條第1項但書以為說明。因此，我國法上法律行為絕對無效與相對無效的區別標準，實際上是以「無效是否得對抗第三人」為判斷。 然而，絕對無效之法律行為是否即得一概對抗第三人，容有疑問，我國法的區別標準應有重新檢討之必要。實則，上述區分諒係亦受日本學說影響至深，日本新民法典制定當時，民法第95條將錯誤之意思表示的法律效果規定為「無效」，但當表意人具有重大過失時，不得主張無效。日本傳統通說認為民法第95條但書以及第94條第2項均屬相對無效。由於我國民法第88條錯誤之意思表示的法律效果係規定為「得撤銷」，因而導致區別標準出現差異。 晚近日本學說逐漸意識傳統的無效概念已無法適應現代交易型態，出現一股模糊無效與撤銷界線的潮流，以「錯誤無效的撤銷化」為起點，從「無效主張者的範圍限制」、「溯及承認的可能性」、「無效主張時間的限制」、「第三人保護」等方面進行調整，以緩和傳統無效概念的嚴格性，並逐步擴展至意思能力欠缺之無效的修正。在此背景下，本文希冀透過梳理日本無效撤銷化學說的發展軌跡，為我國法上無效概念的修正以及絕對無效與相對無效區別標準的檢討提供可能的參考方向。

When a juridical act is void, traditional doctrines have long held that it means the act is “void from the beginning, automatically, and definitively without legal effect.” Moreover, voidness is generally regarded as “absolute” in nature—meaning that anyone may invoke the voidness of such an act, and it may be asserted against anyone. This view appears to originate from early scholars referencing Japanese literature and has since been widely accepted and transmitted through generations of legal academia, forming what can now be described as the prevailing theory. In Taiwan’s traditional doctrine, void juridical acts are further categorized into “absolute voidness” and “relative voidness,” with Article 87, paragraph 1, proviso of the Civil Code cited as a representative example. Thus, in Taiwanese law, the distinction between absolute and relative voidness is effectively based on whether the voidness can be asserted against third parties. However, whether a juridical act deemed absolutely void can always be asserted against third parties remains open to question. The existing standard of distinction in Taiwanese law therefore warrants reexamination. In fact, the said distinction is deeply influenced by Japanese legal theory. When the current Japanese Civil Code was enacted, Article 95 stipulated that a declaration of intention made in error would be “void,” but that voidness could not be asserted if the declarant had gross negligence. Traditional Japanese doctrine has treated both the proviso to Article 95 and Article 94, paragraph 2, as instances of relative voidness. Since Taiwanese law, in contrast, defines the effect of an erroneous declaration of intention under Article 88 as “voidable,” the criteria for distinguishing types of voidness diverge between the two jurisdictions. In recent years, Japanese scholarship has increasingly recognized that the traditional concept of voidness is no longer suited to the realities of modern transactions. A shift has emerged toward blurring the line between voidness and rescission—what has been described as the “rescissionalization of voidness due to error.” This shift is reflected in developments such as limiting the range of parties entitled to assert voidness, allowing retroactive validation, restricting the period during which voidness can be claimed, and enhancing the protection of third parties. These adjustments aim to soften the rigidity of the traditional concept of voidness and have gradually extended to revisions concerning the voidness of acts lacking mental capacity. Against this backdrop, this paper seeks to trace the trajectory of Japanese legal scholarship’s shift toward the rescissionalization of voidness, with the aim of offering potential reference points for revising the concept of voidness in Taiwanese law and reevaluating the standards used to distinguish between absolute and relative voidness.