The author discusses the analytic work on which he based two conferences given on June 29 and July 6, 2005, as part of the "Aristotle, Philosopher for These Times" cycle organized by the Center for Public Studies (CEP). According to the author, Aristotle starts his political theory with a dual genealogy of the city (polis): nature and the work of the legislator. From that premise, Aristotle homologates political justice and the constitution, understood to be the organization of the city. From that homologation there follows an argument that seeks to demonstrate that the basic principles of the constitution are the fundamental criteria in adjudicating political power among citizens. And citizens will exercise that power through participation in democratic deliberation and decision-making. In this field, the author analyzes the Aristotelian conception of co-deliberation and the rhetorical discourse available to it as a means of expression.