The theory of affections has seen a renewed conceptual interest both in the role played in the formulation of power structures in modernity, which remains important in understanding the present form of Nation State, and in the possibility to formulate a new interpretation of the social relationship useful to surpass the classical psychological lectures. We aim here to reconsider an affect which in contemporary language is tinged with theological nuances: the affect of fides. We can translate the word using the modern terms of trust and belief, but also loyalty. The choice of this particular affect is due to the centrality that, in our view, it occupies in modern contract theories, and to its ability to reflect, with its multiple conceptual stratification, different perspectives and political proposals. In order to clarify the terms of this discussion, we will henceforth use the term fides, alongside with different meanings which overlap within it, to illustrate two different and divergent proposals that have emerged during the seventeenth century. We consider, in particular, the thought of Spinoza opposed to the social contract theories by Hobbes in order to understand the modern theoretical break with previous political concepts; in particular, we will briefly analyze the different conceptions of Societas civilis that emerge from this division. The background of these considerations is the analysis of modern philosophy‘s use of the theory of affections. The XVII century witnessed the rise of social contract theory. It draws on the concept of the individual, conceived as isolated from others, located in the original state of nature (pre-social), unable to develop its rational part. It is therefore a victim of its own passions, but even more so those of others. The dominant sentiments emerging in Hobbes‘ Leviathan are therefore those of awe and fear. They derive from the constant uncertainty of one‘s power and strength; the uncertainty of being able to maintain everyone‘s domination over others and thus to suffer in turn the others‘ power. From the necessity to control these emotions in a rational way emerges the contractual proposal to transfer the power to an authority (singular or plural) whom all subjects must obey. Philosophical movements such as neostoicism and philosophical works such as Les passions de l‘ame by Descartes, testify in their „rationalist“ proposal the need to keep a constant control over the passions. They open the way for the famous dialectics of reason and passion, a central theme throughout the Enlightenment. This need to dominate the passions arouses from the complex Cartesian metaphysical theory and from its conception of the individual always split between body and soul, reason and instinct. These two models are the ones which have prevailed; this conception of individual and society and this approach to the passions still dominate common sense when we talk about human affections. The paper follows an itinerary across three authors of the modern age. At first we try to delineate the theory of affection by Descartes, and the birth of the dichotomy of body and soul through the focus of two of the most important works by Descartes: Méditations métaphysiques and Traité sur les passions de l‘âme. Then, by analyzing the works of Hobbes (Leviathan), and Spinoza (Ethic and Political treatise) we will describe in which terms the subject carrying his affective baggage interacts in a political space.
