Descartes not only had a theory of passions, but one that deserves a place among contemporary debates on emotions. The structure of this dissertation attempts to make explicit the unity of that theory. The study of the passions by the physicien (who not only studies matter and motion but also human nature) [Chapter 2] appears to be the "foundations" (as he tells Chanut) of morals [Chapters 1 and 4] insofar as their main function [Chapter 3] is to dispose us to act in ways which directly affect our natural happiness. In other words, Descartes is in the Passions of the Soul (1649) climbing the very tree of philosophy he presented two years earlier in the Preface to French Edition of the Principles of Philosophy: the trunk (in this case a section of it: our nature) leads us to the highest of the three branches (morals) when we study human passions. Human passions constitute the only function of the mind-body union that can guide us in the pursuit of our (natural) happiness. They do this (1) by informing the soul about the current state of perfection both of the body and, most importantly, of the mind-body union; (2) by discriminating what is relevant in the world regarding our perfection; and (3) by proposing (to the will) possible ways of action (i.e. by disposing us to act). The virtuous (the generous) are those who have achieved "contentment" not by impeding the arousal of their passions but by living them according to reason, that is, by following freely the dispositions to act (brought about by them) which can increase our perfection—i.e. the disposition to join true goods and to avoid true evils. Regarding current debates on emotions [Chapter 5], Descartes' perceptual model not only provides a satisfactory answer to the major challenges faced today both by feeling theories (intentionality) and judgment theories (feelings and the passivity of emotions) but it can also help advance those debates by, on one hand, bringing into them new or neglected ideas, and, on the other, providing a solid overall framework to think about passions
