4. Periculum Emptoris (a) Consensual Contracts of Sale in Roman Law

New and interesting insights can even be gained in areas which have traditionally attracted much more scholarly attention than set-off or restitution for improvements. Periculuni est eniptoris is a rule of Roman law that can still be found in modern legal systems.^[335] Once again, however, what worked well in Roman law does not provide a reason­able solution in modern law.

Justinian's compilers took over the risk rule of classical law. At the same time, however, they demolished one of its cornerstones. For, on the one hand, they converted the clas­sical concept of custodia into a fault-based liability: liability for accidents which can typically been avoided (i.e. for all accidents except for vis maior) was turned into the duty to display the strictest diligence.⁶⁴ On the other hand, the compilers generalized the idea that the degree of diligence one party to a contract may reasonably expect from the other is to be determined by considerations of 'utility' (Util- itatsprinzip)⁶³ In view of the fact that a contract of sale bene­fits both the seller and the buyer, it was bound to appear unreasonable to subject the seller to a liability that was stricter than normal.

(1998) 6 ZEuP 651 if., 664 f. Periculum est entptoris also still applies in modem South African law; for all details, see Bauer, 185 if.

⁶⁰ See Law of Obligations (n. 40) 287 in connection with 192 if.

^M See ibid. 290 f.

⁶² Qtti habel eommoda fern debet onem (see Paul. D. 50,17,10 and Law of Obliga­tions (n. 40) 290 f.).

For details, see Law of Obligations (n. 40) 236 ff„ 239 i.

^M See, e.g., Gai. D. 13, 6,18 pr.; Gai. D. 44, 7,1,4.

⁶⁵ See Law of Obligations (n. 40) 198 ff. reduced to culpa.⁶⁶ But this meant that the balance of risks inherent in the classical sale was upset considerably.

(b) The Development of the Generic Sale

The medieval jurists tied the Roman risk rule even more rigorously into a liability system dominated by the fault principle and considerations of utility. At the same time, they started to remove another of its cornerstones. As a result of a "productive misunderstanding', they abandoned the idea that a consensual contract of sale could only relate to a specific object and read the (purely) generic sale into the sources of Roman law.⁶⁷ They thereby ensured that emptio-veiiditio became, and remained, the legal garment for the most important transaction of business life. But they also saddled the discussion of sales law for many centuries with the conceptual consequences of their misunderstand- ing.^hS One of these consequences was a new double mean­ing of the concept of risk: does the seller still have to deliver another object of the same class if the one that he intended to deliver is destroyed (Leistungsgefahf); and does the purchaser still have to pay even though he does not receive the object he has bargained for (Gegenleistungsgefuhr)? The application to generic sales of a set of rules devised origi­nally for the sale of specific goods led to considerable controversy and complex distinctions. All these distinctions and discussions, however, could only imperfectly hide the fundamental truth: periculum est eniptoris was no longer justifiable on rational grounds.