The idea that a simple unilateral promise, until it is accepted, is not binding according to natural law is defended by Grotius in his major work with an argumentation drawn directly from Lessius, an important source of inspiration for the Dutch jurist, who in turn solves the dispute rooted in the tradition of ius commune. This article aims to reconstruct, in its essential stages, an itinerary through the main positions of medieval and early modern civil and canon lawyers about this controversial issue. These sources constitute the background of early modern scholastics and Grotius as well. The paper analyses some of the principal texts of both bodies of law, highlighting arguments and adding new findings. Notably it is shown that Lessius’s and Grotius’s statements represent a turning point, as far as they react against the resumption of the theory of the binding force of simple unilateral promises in the sixteenth century. With Lessius and Grotius, on the other hand, acceptance became a necessary requirement for every transfer of rights and duties to be enforceable.

格罗蒂乌斯（Grotius）在他的主要工作中辩护说，一个简单的单方面的承诺直到被接受才符合自然法律的主张，并直接从莱瑟乌斯（Lessius）提出了论点，莱瑟乌斯是荷兰法学家的重要灵感来源，后者解决了这一问题。争议源于公社的传统。本文旨在在关键阶段通过中世纪和早期现代民法和佳能律师的主要立场来重建有关该争议性问题的路线。这些资源也构成了早期现代学术和格罗修斯的背景。本文分析了两个法律体系的一些主要文本，突出了论点并增加了新的发现。值得一提的是，就莱斯乌斯和格罗蒂乌斯的说法而言，它们代表了一个转折点，因为它们对十六世纪简单单边诺言的约束力理论的恢复做出了反应。另一方面，在Lessius和Grotius的帮助下，接受成为每项权利和义务转让都必须强制执行的必要条件。