In Martin Heidegger's phenomenology, affects do not appear as part of an additive conception of the self, 'notionally separable' elements of an entity whose other element, reason, could be independently analyzed. Aspects of the care structure can be understood only in their phenomenological unity. Thus Heidegger warns that philosophy goes astray when it measures affective phenomena against 'the apodictic certainty of a theoretical cognition of something which is purely present at hand'. Regarding the ontological roots of reason, this chapter argues that Division Two of Being and Time represents Heidegger's phenomenological reconstruction of the concepts of autonomy and responsibility, it thereby uncovers the conditions thanks to which anything can appear as the author's reason for believing something or acting in some way. When Heidegger talks about becoming master of our moods through reason and will, he does not attend to the distinction between moods as existential feelings and moods as emotions or affective intentional states.