Dreams Born and Shattered 365the emergence of the empirical variant as the leading version. Th e common-
will theory largely faded from the scene, for two reasons. One was that its
prewar champions turned their attentions in other directions. Triepel
largely abandoned international law, in favor of his other interest, constitu-
tional law. Anzilotti remained very much on the international-law scene, as
a judge on the World Court. But he underwent an important change of posi-
tion that, as will be presently seen, entailed abandoning some key tenets of
the common- will position. Voluntarism, in its nineteenth- century splendor,
also largely faded, for lack of prominent supporters. Lasson was now dead.
Kaufmann continued to be active— but, like Anzilotti, in rather diff erent
intellectual directions than before.
One of the most prominent writers in the empirical positivist tradi-
tion— to the point that he could be considered the embodiment of main-
stream positivism— was the German Karl Strupp, who was professor of law
at the University of Frankfurt. He frankly described himself as “a pure-
blooded positivist.” Strupp even gave as succinct a statement of the main-
stream positivist credo as has ever been set forth:Public international law is a law between states, not above them. Th e
states being equal among themselves, public international law is a law
of coordination and not of subordination. Important consequence: Th e
states are only bound by norms which they have freely and voluntarily
accepted.More specifi cally, Strupp was a champion of the empirical variant of posi-
tivism, explicitly voicing a lack of confi dence in both the common-will and
voluntarist theories. In the spirit of Hall, whom he explicitly cited, he con-
tended that the real basis of international law is a factual one: the phenom-
enon of reciprocity. Reciprocity, he was careful to explain, is not itself a le-
gal norm. It is a fact of social life, which serves as the foundation of all legal
norms. Its origin, in Strupp’s opinion, was strictly utilitarian, arising out of
the rational self- interest of the actors— out of “pure egoism,” as he put it.
Th e principle of pacta sunt servanda was described as, in its inception, “a
prejudicial norm,” with the sense of legal obligation maturing only later.
Strupp hastened to assure his readers that this thesis, most emphatically,
was not an endorsement of natural law because that extralegal basis lay