Richard Posner, adept of the economic analytical criterion of law, parameterized the development of his Theory of Law in the construction of judicial decisions, developing, for that purpose, a study full of interdisciplinary elements described in the legal and economic sciences, seeking, with this, describe a stable and safe scenario for the application of the law. In this way, the present dissertation will present, in its first chapter, the fundamental elements of economic sciences, especially its concept of efficiency, whose scope will be essential for the development of Richard Posner s work, in the second chapter the work will turn its gaze to the development and unfolding of the American author s thought, demonstrating the beginning of his investigative process until its pragmatic turn, provoked, above all, by Ronald Dworkin s interventions and criticisms, reaching, finally, the third chapter where the object of investigation will be the process of metrification of legal thought, demonstrating the theory of maximization of wealth developed by Posner and evidencing the reasons why the author disowned the work of Pareto and Kaldor-Hicks. In its conclusion, this dissertation will demonstrate the evolutionary process of Richard Posner s thought, in particular the process of metrification of efficiency based on the maximization of wealth, which will base the decision-making process of the Judges and will promote, according to his vision, the construction of the Theory of Law.