This article aims to retrace the genesis of the capability approach as a new development model based on the expansion of freedoms. It attempts to shed some light on Amartya Sen's critical dialogue with utilitarianism, social choice theory, and the theory of justice in order to stand out through his own approach that unites ethics and economics. Points of over lap between these theories are raised, but also the sources of divergence around the question of justice in the assessment of individual advantage.