雙務關係牽連性之理論基礎與其展開

Abstract

雙務契約牽連性的概念，歐陸各國法均有之。台灣的學說實務多半認為，雙務契約牽連性僅指涉「完全雙務契約」上立於對價關係的主給付義務。依此，台灣民法第264條之同時履行抗辯權、第266條之危險負擔一般規定，在體現出功能上、存續上牽連性的同時，其範圍理論上也要隨同學說實務對雙務契約牽連性的理解，限於完全雙務契約上立於對價關係的主給付義務。

牽連性之語源Synallagma，在羅馬法文上並沒有與對價關係形成必然之連結，其至多僅說明契約之債之成立。附負擔贈與等非現代意義之完全雙務契約，在羅馬法案例適用上，也是Synallagma所處理之對象。Synallagma與完全雙務契約之履行之連結，一直到自然法時期才藉由「條件理論」確立，並由德國和部分法國、日本學說所承繼（交換關係牽連性）。但同時，遵循羅馬法，主張不須對價關係的學說，也一直存在，隨後成為法國、日本另一股批判對價關係的學說潮流（法的牽連性）。

「一方不為給付，另一方即無須給付」之條件理論，除了是同時履行抗辯權和危險負擔一般規定的源頭，也是契約解消之鼻祖。台灣現行民法將「契約解除」獨立成乙節，並不妨礙契約解消在歷史上與牽連性理論之淵源。然而，不管是國際契約法的趨勢，還是台灣本土的不完全給付解除理論，均認為解除權不以對價關係之主給付義務為限。相對於此，與解除權同源的同時履行抗辯權和危險負擔一般規定仍自限對價關係之思想，其正當性即有待檢視。

其實，交換關係牽連性之所以限於「對價關係」，乃因其以類型化之交換目的，解釋當事人在一方未依債之本旨給付時，另一方所欲採取的救濟行動。相對於此，法的牽連性能更廣泛地探問雙方當事人之共同主觀目的。台灣學說常以「契約解釋」判斷系爭目的之達成是否為雙方約定為給付之人所能保有給付之條件，就牽連性的解釋上，應較類似於法的牽連性之理解。準此，除不完全雙務契約可以進入雙務關係牽連性的論述範圍，但凡雙方當事人有共同目的，無論其為無因管理、占有回復關係，亦或是相鄰關係，法的牽連性也可以構築該目的挫敗時如何應對的理論基盤。

The concept of Synallagma in bilateral contracts is widely recognized in legal systems across Continental Europe. In Taiwan, literatures hold that Synallagma applies exclusively to the primary contractual obligations established on the basis of a quid pro quo relationship in perfectly mutual contracts. In this sense, being the very epitome of Synallagma, the exception of simultaneous performance (Article 264 of the Taiwan Civil Code) and the general provisions on risk allocation (Article 266, known as “Gefahrtragung” under German law) should, theoretically, align with the said interpretation.

The term Synallagma has its origins in Roman law, where it did not imply a necessary connection to a quid pro quo relationship--it merely implicates the creation of contractual obligations. Contracts not fitting the modern sense of a perfectly mutual contract, such as gifts with charge, were also governed by Synallagma in Roman practice. It was not until the natural law period that Synallagma came to be firmly associated with prestation in perfectly mutual contracts through the “conditions.” This interpretation was carried forward by German and certain French schools of thought as the “exchange theory” (Austauschgedanken). In parallel with this trend, part of the French jurisprudence refers to Roman law and contends that reciprocity does not necessarily have to be conditioned to a quid pro quo relationship. This is the countercurrent known as the “theory of legal reciprocity.”

“If one party does not perform, the other party is excused from performance”—this very condition underpins the historical origin of the exception of simultaneous performance and the Gefahrtragung. It also laid the foundation for the termination of contract. Although Taiwan Civil Code treats termination of contract as an independent section, such a historical link cannot be overlooked. However, despite having the same origin, literatures only allow termination when the object of malperformance turns out to be secondary or affiliative contractual prestation. Up to now, no literature has justified the reason why the exception of simultaneous performance and Gefahrtragung cannot be interpreted in the same way.

In fact, the “exchange theory” limits Synallagma in a quid pro quo relation because it presumes one would want to refuse to give when the other fails to perform. This presumption becomes a classical categorization of the parties’ will which has already overlooked the real party will in respective cases. In contrast, the “theory of legal reciprocity” examines the common subjective purpose of both parties. Taiwanese literatures often emphasize that the interpretation of common subjective purpose should be carried out through “contract interpretation,” and such thought, in fact, aligns more closely with the “theory of legal reciprocity.” Accordingly, even non-perfectly mutual contracts could fall within the scope of Synallagma. As long as both parties have common purposes, any sorts of legal relationship established between them can be referred to as Synallagma, be it a stipulated relationship as spontaneous mandate, possessory recovery, or adjacency rights.