The paper contradicts the impossibility of reconciling the legal perspective and the law and economics of law perspective in relation to the reasons of the mandatory rules in contract law, the paper argues that the existence of these rules is based on the economic ideas rather that in the legal view. In addition, the paper argues that the reasons that support the existence of mandatory rules in contract law do not justify the existence of default rules in the same area of law. At this point we argue that legal literature describes the purposes of default rules in contract law, but these purposes only have sense if they include the assumption of invariable incompleteness of contracts based on Abogado Universidad de Los Andes (99'), Especialista en Derecho Contractual de la Universidad Externado de Colombia y Maestria en Derecho Economico de la Universidad de Chile. Docente Investigador del Departamento de Derecho Economico de la Universidad Externado de Colombia en temas de analisis economico del derecho y behavioral law and economics. Contacto: daniel.monroy@uexternado.edu.co the presence of transaction costs in the markets. The existence of positive transaction costs is an idea that has not been generally assumed by the legal literature, but which allows new areas of research in contract law not studied locally.
