Experimental studies on willpower confirm the Strength Model of Self-Control, which claims that willpower depends on limited physiological resources. Exercising willpower depletes these resources, which impairs further exercises of willpower. This phenomenon is called “ego-depletion.” As a result, depleting these resources impairs further exercises of executive control. My thesis argues that this phenomenon has two important philosophical consequences: First, ego-depletion provides evidence against the Humean approach to motivation, according to which people always act according to their strongest desires. Second, people suffering from ego-depletion are not fully responsible for failures of self-control