This translation is a selection from Lessius' treatment of contract law in his larger work On Justice and Right. By drawing on diverse sources ranging from Roman and canon law to moral philosophy, Lessius offers practical advice in commercial and financial matters. These chapters on sale, securities, and insurance engage perennial questions concerning the lawfulness of insider trading, the sale of toxic debt, and asymmetric information in insurance markets.Translated by Wim Decock and Nicholas De Sutter.