.
Thus the Romans spoke of them as modes of "natural acquisition" by
occupation or by specification (making a species, i.e., creation).
Indeed, taking possession of what one discovers is so in accord with a
fundamental human instinct that discovery and occupation have stood in
the books ever since substantially as the Romans stated them. A
striking example of the extent to which this doctrine responds to
deep-seated human tendencies is afforded by the customs as to
discovery of mineral on the public domain upon which American mining
law is founded and the customs of the old whale-fishery as to
fast-fish and loose-fish which were recognized and given effect by the
courts. But there is a difficulty in the case of creation or
specification in that except where the creation is mental only
materials must be used, and the materials or tools employed may be
another's. Hence Grotius reduced creation by labor to occupation,
since if one made from what he discovered, the materials were his by
occupation, and if not, the title of others to the materials was
decisive. This controversy as to the respective claims of him who
creates by labor and him who furnishes the materials goes back to the
Roman jurists of the classical period. The Proculians awarded the
thing made to the maker because as such it had not existed previously.
The Sabinians awarded it to the owner of the materials because without
materials the new thing could not have been made. In the maturity of
Roman law a compromise was made, and various compromises have obtained
ever since. In modern times, however, the claim of him who creates has
been urged by a long line of writers beginning with Locke and
culminating in the socialists. The Romans spoke of what one acquired
under the prevailing social, economic or legal system as held by
"civil" acquisition and conceived that the principle _suum cuique
tribuere_ secured the thing so acquired as being one's own.

Roman jurists recognized that certain things were not subject to
acquisition in any of the foregoing ways. Under the influence of the
Stoic idea of _naturalis ratio_ they conceived that most things were
destined by nature to be controlled by man. Such control expressed
their natural purpose. Some things, however, were not destined to be
controlled by individuals. Individual control would run counter to
their natural purpose. Hence they could not be the subjects of private
ownership. Such things were called _res extr