This work appraises the tasks generally attributed to economics: description, explanation, prediction and prescription of economic phenomena. It will be shown that the last one, the normative task, has great relevance. Thus, the normative character of economics will be deduced from rationality, and what is the most adequate rationality for economics will be analyzed. Finally, the relationship between ethical theories and the normative character of economics will be addressed.En este trabajo se hace una evaluación de las tareas habitualmente asignadas a la ciencia económica: descripción, explicación, predicción y prescripción de fenómenos económicos. Se mostrará que la última de éstas, la normativa, tiene una gran importancia. Para hacerlo s...