It is AD 212. You are a jurist consulting in Rome. Crassus, a senator and wealthy landowner, tells you the following story:
             A few months ago I came down with a debilitating fever. My doctor Medicus, whom I now know for a thorough villain, told me I was suffering from nervous exhaustion caused by my owning too much property. He said it would assist my recovery if I made over to him a large portion of my property. I accordingly mancipated to Medicus four of my estates. Medicus proceeded to mancipate one estate to his wife and another to his elder son. The third estate he handed over to his younger son but without formal conveyance and the fourth he kept. Another doctor has now cured me of the fever. I want to know what I can do about recovering my estates.
             It is important in this situation to look at the legal effects of Crassus mancipating four of his estates to Medicus. In the mancipation of res mancipi, ownership was transferred unconditionally (except that the transferor could reserve a servitude over the property) and immediately, and it could not be postponed to take effect at some future time. Provided that the mancipatio was correctly performed, the conveyance could not be impugned on grounds such as fraud or duress, meaning that the object of the transaction passed ownership irrespective of such considerations.
             The situation points to the unjust enrichment of Medicus, and thus we must look at a possible condictio. If a person mistakenly transferred a thing to another, wrongly believing that the transfer was owed, the transferor had the condictio indebtii (the recovery of a thing not owed) for its recovery. Crassus would have to show that he made a transfer, and that the obligation was not owed. However, the action was not available if the transferee had acted in bad faith, as that would amount to theft, for which there were other remedies. Therefore it would seem that, even though the condic
             ...