y does not exist or does not busy itself with continuous
legislation, then the above-named factors exercise a more direct
influence upon the development of law, should there arise in actual life
an imperious demand for definite rules of law. The theory of natural law
was only the mirror held up by legal philosophy, in which the rays
emitted by these factors were focused into a homogeneous image.

[Sidenote: Positive international law.]

5. That, by the side of his international law, with its basis in natural
law, there was also a positive international law, was not unrecognized
by Grotius, but his purpose was merely to depict a system of
international law which should compel universal observance irrespective
of time and nation. And shortly after Grotius, Zouche and his followers
did indeed attempt, in opposition to him, to formulate just such a
positive international law, but it could not win for itself, at any rate
in the seventeenth century, any great recognition; development was
overshadowed by the system of Grotius, and many of his rules of natural
law gradually obtained recognition in practice as customary law. But the
increasing intercourse of states in the eighteenth century called forth
a more positive school of international jurists, and the works of
Bynkershoek, Moser, and Martens fertilized the soil on which in the
nineteenth century there could gradually grow a really positive theory
of international law, even if the scales which betoken its past
connexion with natural law still adhere to the international law of
to-day.

[Sidenote: International legislation initiated by the Congress of
Vienna.]

6. A positive theory of international law was demanded by the fact that
in the first quarter of the nineteenth century, with the Final Act of
the Congress of Vienna, the quasi-legislative activity of international
conventions asserted itself for the first time. From then onwards,
general international law was frequently evolved by means of an
international convention. It was in this way that the permanent
neutralization of Switzerland, Belgium, and Luxemburg was effected, the
navigation of the so-called international rivers in Europe declared
free, the slave-trade abolished, the grades of diplomatic agents
regulated, privateering abolished, the necessity of effectiveness in a
blockade recognized, the principle 'free ships, free goods' finally
established, neutral goods on enemy ships declared free, rules pro