 According to Roman law, as formulated in the Code of Justinian, “ownership” and “legitimate use” cannot be permanently separated. For example, it is one thing for me to own a book but to let you use it for a while. Ownership in that case means that I can recall the book, and even if I do not do so, you should return it to me when you are done with it. But it is quite another matter for me to own the book but to grant you permanent use of it, to agree not to recall it as long as you want to keep it, and to agree that you have no obligation to give it back ever. John XXII points out that, from the point of view of Roman law, the latter case makes no sense. There is no practical difference in that case between your having the use of the book and your owning it; for all intents and purposes, it is yours.