Most, if not all, systems of law are compelled by the very nature of things to distinguish landed from all other types of property, for land is necessary for the production of food and the erection of dwelling-places, and, unlike other things, it cannot be moved. In English law, in the guise of the distinction between "real" and "personal" property, this contrast is particularly marked; in Roman law, though it existed as early as the XII Tables (1), its importance is overshadowed by a different and purely Roman distinction, that between res mancipi and res nec mancipi.
Res mancipi were land subject to Roman ownership (2), slaves, beasts of draft and burden, including cattle, and rustic servitudes belonging to land subject to Roman ownership; res nec mancipi were all other things. In the developed law the point of the distinction is that full Quiritarian ownership in res mancipi can only be transferred by the solemn method of conveyance known as mancipatio or the equivalent ceremony of in iure cessio, whereas the ownership of res nec mancipi can be transferred by mere delivery (traditio). Thus if A wants to make B the gift of a sheep and delivers it to him for that purpose the sheep becomes immediately the full Quiritarian property of B, but if he wants to give him an ox and does the same the ox remains the property ex iure Quiritium of A, because an ox is a res mancipi whereas a sheep is not.
It is not difficult to see some reason why the particular classes of things known as res mancipi should have been specially treated; they are the things which are most important for the peasant proprietor, the land, the slaves and beasts with which it is worked, and the rights of way and water without which an estate, if it is away from the public road or has no water on it, cannot well be farmed. Such things must not pass from hand to hand as less important things may; if the ownership in them is to change there must be a public act of transfer of which witness can afterwards be given in case of any dispute (3). Nevertheless it is probable that the category of res mancipi as it appears in the developed law is not exactly the same as it had been in some earlier period. It has been pointed out that the ceremonial of mancipation is not at all appropriate to a conveyance of land, because it includes the grasping of the thing to be acquired by the transferee and the grasping of land is an impossible, or at least an undignified, gesture. And it may well be that the reason why land was not originally included among the res mancipi was that it was not capable of private ownership, or if capable of ownership, was not alienable but had to descend from father to son. We know that very early law does not as a rule recognise private property in land; among the Germanic tribes, for instance, it was unknown in Caesar's day, and even in the time of Tacitus it existed only for the homestead, the remainder of the land being owned by the village community as a whole and redistributed to individuals for cultivation every year. Traces of original clan or tribal ownership are also to be found in Greek law, and indeed, so long as there is plenty of land for everyone who can till it, and a great part of the available land is necessarily left fallow each year because the proper use of manure is unknown, the desire for individual ownership will hardly make itself felt. It is then likely enough on a priori grounds that there was a time at Rome also when land, or the greater part of it, was not owned privately, and this probability is supported by the tradition that at the foundation of the city Romulus distributed a "lot" (heredium) of two iugera to each citizen. As this would not be nearly enough to support a family the distribution would imply that there existed also some form of communal cultivation, the heredium being the homestead merely, and very probably, as its name seems to imply, inalienable. But this tradition is not particularly trustworthy (4), and in any case we do not know what form the communal ownership of the remaining land took, whether it was distributed among the different gentes, as is most probable, or among some other subdivisions of the state. At the time of the XII Tables at any rate, it is clear that private property in land already existed and was not confined to the heredium; the definite rule for the usucapion of land is sufficient evidence, and indeed the early history of the struggle between the orders (5) is incomprehensible without this assumption.
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(1) The times for usucapion are different according as the thing in question is mobilis or immobilis.
(2) After the extension of citizenship to the whole of Italy this meant all land in Italy, but when the citizenship was further extended the deduction that the land of the new citizens was capable of Quiritarian ownership was not drawn. Occasionally however land in the provinces might be assimilated legally to land in Italy by grant of the ius Italicum.
(3) Perhaps res mancipi were originally the only things which counted for assessment to the census.
(4) It may be a dating back of what occurred in quite different circumstances when colonies were founded.
(5) The struggle was to a certain extent one between rich and poor and in early times this can only mean those who are rich or poor in land. It is however possible that land remained inalienable even though privately owned.
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Source:
Historical introduction to the study of Roman law, H. F. Jolowicz, pages 139 - 141.
