The question ‘Why be rational?’ could be calling into question a commitment to respond to the requirements of subjective rationality, or could be calling into question a commitment to respond to objective reasons. I examine the question in this second sense, placing it in the mouth of the arationalist — an individual who has not ruled out the possibility of not acting or believing on the basis of objective reasons. In evaluating responses to the arationalist’s question, I consider the replies (...) of three philosophers, where these exemplify a shared conceptual strategy: to claim that reasons-responsiveness is self-justifying. I argue that each reply fails, and that the overall strategy is not only dialectically ineffective against the arationalist but is also ineffective even for the goal of reassuring those already committed to reasons-responsiveness. The question ‘Why be rational?’ is yet to be answered, and so a commitment to respond to objective reasons is ungrounded. (shrink)