"Solutio propria", "in praecisa forma et specie obligationis"[3885] (to use the terminology of the European ius commune) has always been, and still is, the most important way of terminating obligations.

Datio in solutum and release have been mentioned as two forms of what was usually referred to as "solutio impropria". But there was a whole variety of further situations which entailed the extinction of an existing obligation.

Novatio was one of them: the old obligatio was translated into a new one (always a stipulation), with the effect that the former fell away ipso hire.^[3886] Litis contestatio had a similar effect, at least as far as iudicia legitima were concerned: the original obligation was dissolved by operation of the law (ipso iure), and the defendant became bound to respect any condemnation that might ensue (condemnari oportere).^[3887] As a result, the plaintiff was prevented from enforcing the old (now extinct) obligation a second time. Confusio brought about the end of an obligation, and so did concursus causarum. Confusio refers to the situation where the position of debtor and creditor with regard to one and the same obligation merge in one person;^[3888] this can occur, for instance, if the debtor becomes the creditor's heir or if—conversely — the creditor succeeds his debtor. After all, it is essential for an obligation that it establishes a legal relationship between (at least) two different parties.^[3889] Concursus causarum was the concurrence of two or more titles of acquisition concerning one specific thing in one and the same person.^{[3890] [3891]} If somebody was entitled to receive delivery of a particular sedan chair by virtue of both a stipulatio and a contract of sale, one of the obligations had to fall away, for the creditor could, after all, receive delivery only once. If he had acquired the sedan-chair by traditio under the stipulation, he could not afterwards bring the actio empti for the same object; in this particular instance, that already followed from the more specific rule of "suae rei emptio non valet".⁸³ This brings us into the vicinity of another reason why an obligation could fall away: supervening impossibility in general had that effect, provided the debtor could not be held responsible therefor. Impossibilium nulla obligatio: if performance was initially impossible, an obligation could not come into existence;^{[3892] [3893]} impossibility occurring after conclusion of the contract made it fall away again.⁸' And as we find the former of these principles codified in § 306 BGB, so § 275 BGB still formulates the basic proposition concerning supervening impossibility in the following words:

"The debtor is relieved from his obligation to perform if the performance becomes impossible because of a circumstance, for which he is not responsible and which occurs after the creation of the obligation."

III.

More on the topic "Solutio propria", "in praecisa forma et specie obligationis"[3885] (to use the terminology of the European ius commune) has always been, and still is, the most important way of terminating obligations.:

1. Unenforceable obligations ("obligationes naturales")
2. OTHER FORMS OF "SOLUTIO IMPROPRIA"
3. 2. From "Konsumptionskonkurrenz" to "Solutionskonkurrenz"
4. "Quod metus causa gestum erit, ratum non habeo"
5. 1. Restoration, damages and "Dtfferenztheorie "
6. 1. The "iron" rule of Roman law and the notion of an implied lex commissoria
7. "De facto" contracts and implied promises
8. "Animus iniuriandi" and Artemus Jones
9. Essential elements of Roman "labour law"
10. Causa as an extra piece of "garment"
11. 2. The "natural" law of delict
12. "Si paret... dare oportere"
13. The limits of the notion of "corrumpere"