給付目的不達不當得利

Condictio ob rem

羅馬法具有訴求力之契約有限，他方受領給付卻不為對待給付，一方若無法訴請履行，為保護先為給付之人遂賦予目的不達返還訴權。一旦契約原則上具有訴求力之原則確立，此訴權應功成身退。德國民法雖有目的不達不當得利之明文，但學說多認為應嚴格其要件，限制其適用範圍，給付目的是否達成為契約解釋，而非不當得利法規定價值判斷的問題。我國不當得利法雖無明文，但學說及實務見解無不肯定之，給付不當得利給付目的之欠缺，有自始無給付目的、給付目的嗣後不存在與給付目的不達三者，目的不達乃「給付原因初固有效存在，然因其他障礙不能達到目的」。經分析檢討相關案例，許多我國最高法院認為屬於目的不達案例，根本不構成不當得利，而屬於傳統所謂債務不履行或違約救濟的問題。目的不達不當得利返還之適用若不加節制，僅以給付所欲達成之結果不生為要件，則將肇至契約救濟體系之紊亂與不當得利返還制度的肥大化，給付不當得利法將成為不折不扣的衡平法。

There was a limited number of actionable contracts in Roman law. In the case of contracts which were in Roman law not binding, parties were left to voluntary performance. If the counter-performance remained outstanding, in Rome the condictio ob rem was available. In spite of the missing of the historic background, this kind of condictio can still be found in the BGB. Today, this condictio has a narrow field of application. It relates to situations where the claimant has provided performance to the defendant not in exchange for counter-performance of another obligation, but for another purpose, and where both parties have agreed that this purpose was the reason for the performance. Some academics have taken the view that condictio ob rem should apply in cases where the parties have performed in anticipation of a contract which is never concluded. A party may likewise have performed under a contract which it knows to be void for lack of form, expecting this lack to be healed by complete performance. The Civil Code of Republic China enacted in the year 1929 omitted purposely regulations concerning condictio ob rem. In spite of that fact, it is widely recognized by legal doctrines and judgements of the Supreme Court. Academics and the Supreme Court have taken the view that a performance which has failed to produce the result at which the transaction had aimed can be recovered. Close inspection of the relevant cases reveals that the cases which courts seek to apply the rules of condictio ob rem are cases of contract law, rather than of unjust enrichment. If we allow restitution whenever the result intended to be achieved by those efforts in accordance with the contents of the legal transaction does not occur, the rules of remedies of contract will be in a state of chaos and the law of unjust enrichment based on performance could be purely and simply a rule of equity.