This thesis argues that Heidegger’s existential analytic of human existence challenges the traditional understanding of responsibility as lying in the power or mastery of the subject. In contrast to secondary literature that attempts to read Heidegger as showing that we take responsibility through some kind of self-determination or control, I argue that Heidegger’s account of our thrownness, and its first-personal manifestation in our attunement, contests such understandings and points to an account of responsibility that does not find its locus in (...) the power of the subject. In light of this, I argue that taking responsibility for our being-in-the-world should be understood as becoming attentive. By emphasizing the ‘movement’ of thrownness and the meaning of this as finding ourselves always already gripped by way of being attuned, my analysis demonstrates the pervasive power of that which is beyond the subject. I show that we must always already find ourselves submitted to particular possibilities and, more fundamentally, to the enigma of being Dasein. From this analysis, and via the work of Harry Frankfurt, I demonstrate how our thrownness speaks against seeing responsibility for our being-in-the-world in terms of choice, rational judgement, or wholeheartedness. A further analysis of anxiety, contrasting with accounts which read it as manifesting a privileged space for freedom and self-determination, emphasizes the revelation of the ‘I’ as essentially bound to what is beyond it. I then argue that a Heideggerian account of responsibility should be understood in terms of attention or attentiveness, a notion that is developed through phenomenological analysis, and in dialogue with the work of Iris Murdoch. Through the use of the examples of the film 'Locke' and the novel 'Disgrace', I propose that attentiveness, with its accent on that which is beyond the subject, is a more appropriate way of conceiving responsibility on a Heideggerian account. (shrink)