Subquestion II: What things are to be restored by reason of the manner in which they were acquired

We have TREATED of goods to be restored insofar as they are considered in themselves; now we must consider those which are unjustly acquired, or possessed under an unjust title. For some are acquired by contracts, in which forms are prescribed which no one can transgress either licitly or validly; and to these contracts persons who are suitable, or capable, are supposed, while others are declared incapable by law. Others are possessed by donation, which likewise has its own rules if it is to be valid. Many things pass into another's ownership by title of prescription, but for this the laws require various conditions, as I shall weigh below. Certain things are given by title of payment for the function of an office, or for meretricious prostitution. Some also, by fowling, hunting, fishing, the use of common things, illicit games, and lastly by unexpected discovery, are taken into the possession and ownership of one person; of these the laws make various determinations. In the following Doubts we must inquire whether, how, and when these things ought to be restored to their proper Owners.