This article analyzes Kant’s theoretical foundations, which represent his moral theory, in order to understand concepts and aspects that are determining for the realms of politics and law. Freedom, autonomy and practical reason are categories that make it possible to grasp the influence of morals on legal and political phenomena. The role of moral principles is to provide universal action rules for all rational individuals regardless of their particular inclinations in the realms of what Kant calls “external” freedom.Keywords: moral theory, freedom, practical reason, law, politics.O presente trabalho analisa os fundamentos teóricos kantianos, representativos de uma teoria moral, para compreendermos conceitos e aspectos determinantes nas esf...