The responsibility for accidental consequences is based on legally established causation extended by an additional cause. This means that by breaching a contract, the obligor creates a situation in the first stage of the causation development that gives rise to damage that occurs in the second stage of the causal development. The damage does not occur as a direct consequence of the action taken by the obligor but due to a certain other (accidental) cause for which the obligor is, in principle, not held legally liable. However, in the event of responsibility for accidental consequences, the obligor is held liable on the ground that he is legally attributed wrongful conduct the result of which is damage. Although the term casus mixtus is not of Roman origin, cases can be traced in the casuistry of sources from Roman law that may qualify today as cases of responsibility for accidental consequences. Within the framework of Roman law, the latter can be found in various types of contracts, e.g. enterprise, lease and loan agreements, and deposita. Contrary to modern civil law codifications, the Roman sources examined do not contain general or abstract legal regulations but concentrate on case-based reasoning. What they all share in common is that they provide for the consideration of causation extended by an additional cause and the resulting responsibility for the accidental damage that occurs in the second stage of the causal development. Several Roman sources also provide for the consideration of a hypothetical cause that would, in a specific ease, (hypothetically) break the causal relationship between the conduct of the obligor and the damage caused. However, there is a single source in which no provision is made of this type of legal causation. According to medieval legal thought, the latter was omitted from consideration and incorporated into the basic principle versare in re illicit, according to which every person who engages in impermissible conduct must suffer all consequences that may arise as a result of their actions. During that period the legal institute was, to a certain extent, abstracted and generalised. During the time when major European civil codifications were being developed, responsibility for accidental consequences was regulated by the Austrian legislator on the basis of the General Civil Code and is also known to the modem Slovenian law of obligations governed by the Code of Obligations. Although the modern civil code is static as opposed to the dynamic casuistry of classical Roman law, there are many substantial and explicit similarities between the casus mixtus cases in Roman law as well as the modern Austrian and Slovenian legal arrangements applied to the institute concerned. Based on the results of the comparative, it may validly be assumed that the aforementioned modern arrangements applied to responsibility for accidental consequences have been developed under the strong influence of Roman law. Therefore, it may also be concluded on good grounds that the institute of responsibility for accidental consequences is a clear case of the reception of Roman legal matter into the modern civil arrangements under examination.
