The Will of the Testator and the clausula “rebus sic stantibus” in the Late Medieval and Early Modern Period: A Path between Doctrine and Practice

The paper addresses the relation between the clausula “rebus sic stantibus” and testamentary dispositions between the late Middle Ages and the early modern age: a relation designed by legal doctrine and legal practice in the effort to balance potential conflicts between the will of the subject and the demands of equity arising from an unforeseen change in circumstances. The testamentary document has always aroused particular interest in legal science with regard to its interpretation, which is necessary for a precise reconstruction of the author’s will after his or her death. In addition to the many rules for interpretation created by Roman and medieval jurisprudence, between the 14th and 15th centuries the implied term represented by the clausula was applied to dispositions of last will in the practice of consilia, after the most significant authors of the ius commune had extended its principle not only to oaths and promises, but also to any other disposition of will. A particular attention is paid to consilium no. 84 by the famous civil and canon law master Petrus de Ancharano, analysing the arguments advanced by him that led for the first time to the extension of the clausula to testamentary matters. The testament emerged thereafter as an important area of application of the principle: doctrine and practice of the late ius commune would continue to recognise its effectiveness even after the general theory of the clausula was challenged (particularly in the field of contract law), first by legal humanism and afterwards by the school of natural law.