1. Impossibilium mil la obligatio est

"A contract, the performance of which is impossible, is void" states the BGB in its § 306, with characteristic precision and uncharacteristic

* On this text, see Kniitel, Stipulatio poenae, pp.

® Ter. Cl. D. 40, 9, 32, 1; Iui. D. 38, 1, 25; Pierre Jauberl, "La Lex Aelia Sentia et la locatio conductio des operae liberti", (1965) 43 RH5 sqq.

® Cf. Paul. D. 37, 14, 6, 1; Ter. Cl. D. 40, 9, 32, 2.

® Paul. D. 38, 1, 39 pr.

dash. luventius Celsus himself, well known for his succinct and trenchant style/'⁸ could hardly have faulted the German version of the famous principle that has come down to us under his name: "Impossibilium nulla obligatio est."^{[3449] [3450] It thus appears to be a rule, not only of venerable antiquity, but also of obvious and even axiomatic validity. It is echoed in other modern legal systems[3451] and corresponds to the maxim "ought implies can" of modern moral philosophy.[3452] If we oblige somebody to do something, we presuppose in fact that he is able to do this act; anything else would be a kind of buffoonery ("lusisse tantum, et nihil egisse cense[m]ur" in the words of Pufendorf).[3453] Impossibilium nulla obligatio est neatly encapsulates the idea that nobody can be obliged to perform what he cannot perform. But this is not identical to the assertion that a contract aimed at an impossible performance is bound to be void: at least in the eyes of the Roman lawyers, the one did not necessarily follow from the other. What, then, was the effect of impossibility of performance on the contractual relationship between two parties in Roman law?}

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