This research examines the treatment that Spinoza gives to the subject of affections and their relationship with ethics: what they are, what is their number, what relationship they have with the power of human action, how their government affects freedom and the happiness of man and what is the power of understanding over them, based on the analysis of the main work of the 17th century rationalist philosopher Baruch Spinoza, the Ethics demonstrated according to the geometric order (1677). In the first place, the historical and philosophical context of Spinoza's thought is established: his time, the foundations of his metaphysics and anthropology; Secondly, the nature of the affects is analyzed, what their number is, and what relationship they have with the power of human action, and, finally, what Spinoza understands by servitude is analyzed, their causes are exits, what is the power of the understanding to moderate the affections, and how his government affects the freedom and happiness of man.