1 88 HARVARD LAW REVIEW. to a sort of classified catalogue where there would be no repetitions or cross references, and the classification would explain itself. Am- bition on that scale is destined to disappointment by the nature of things. Some general divisions in the science of law have been made classical by the method adopted in the Institutes of Justinian, and by the subsequent development given to the Roman ideas by com- mentators and modern jurists. One such division, which has been explicitly prominent only in recent times, is now commonly marked by the terms in rem and in personam. Some duties and rights consist in a claim of one certain person upon another; the duty and the correlated right are alike determinate. In these cases the duties and rights are said by modern writers to be in personam. Other duties and rights do not import any such definite correla- tion. When we put ourselves in the position of duty, we find no certain person having the right; when we put ourselves in the position of right, we find no certain person owing the duty. These impersonal rights and duties, regarding all one's fellow-subjects or a class of them, are said to be iit rem. We have already seen something of this in -endeavoring to fix the conception of legal right. The reason why we cannot well use the English adjectives " real " and " personal " for this purpose is that they are already appropriated to special technical uses with which this would clash. It would be free from objection, however, to speak of personal and impersonal duties or rights. The most obvious and typical example of an event creating rights in personam is a contract. John and Peter agree that John shall sell his house to Peter on certain terms. This gives John and Peter certain rights against each other; they are bound to each other by a tie of mutual claims existing between them and between them only. This definite relation of claim and duty was called an obligatio7t by the Roman lawyer, and is still so called everywhere, save that in English-speaking countries an unfortu- nate habit has arisen of using " obligation " in a lax manner as co-extensive with duties of every kind.^ Now let Peter pay John the purchase money, and John do all proper acts for completing the sale. Suppose, to simplify the illustration, that John has re- 1 In English law the word formerly had a much more restricted meaning ; namely, the special kind of contract also called a bond. But the English name " bond " is now always or almost always used for this, and it is convenient to restore " obligation " to its Roman sense, for which there is no synonym.
