ABSTRACT
This article examines Grotius’s use of a Roman tradition to establish his notion of a natural and international law in his early treatise De iure praedae (1604–1606). It is argued that De iure praedae, on a methodological level, constituted an attempt to introduce a new doctrine of sources of law by making use of the method of classical rhetoric. On a substantive level, the treatise must be seen as growing out of a Ciceronian tradition of natural law arguments in favor of just war, a tradition further enriched by Grotius with concepts taken from the property law of the Digest. These concepts afforded Grotius with the substantive framework to develop his doctrine of subjective natural rights as sketched in the hitherto unpublished early manuscript Theses LVI. An implication of this investigation of the Roman foundations of Grotius’s theory of natural law is that it challenges widespread assumptions about the “positive” character of ancient liberty.
