Leonardus Lessius: De iustitia et iure caeterisque virtutibus cardinalibus. Über die Gerechtigkeit und das Recht und die übrigen Kardinaltugenden. Teil III

In the third part of the 1605 edition of ›De iustitia et iure caeterisque virtutibus cardinalibus‹, Leonardus Lessius offers a concentrated exposition of the late scholastic doctrine of contract law, a highly innovative section of the new Catholic natural law. Against the Roman rule that informal agreements should in principle have no legally binding effect, canon law had from the very beginning placed the principle of the strict binding nature of promises (»pacta sunt servanda«). It was not until the natural law teachers of the 16th century that this idea was systematically developed and rules were formulated in this sense, for example, for the consequences of errors and other defects of will. At the same time, contract law was reoriented towards the will of the contracting parties, i.e. the principle of private freedom of contract. Lessius develops this approach in exemplary consistency, taking special account of new business practices and financial instruments, such as those developed on the stock exchanges of Antwerp and Frankfurt.