 The requirement of universality or followability sets minimal constraints on processes that count as reasoning (O’Neill 2015: 3). By following this reasoning, we find out that no plurality of agents can choose to live by principles that aim to destroy or undermine the agency (of whatever determinate shape) of some of its members (O’Neill 1989a: 10; see also O’Neill 1989b, 2015). As a result, practical reasoning justifies the prohibition to harm, coerce, and deceive others. This is not to say that by appealing to the requirement of followability we can solve all problems and fully determine the content of all duties. On the contrary, O’Neill thinks that there are large varieties of moral issues for which we need to offer more substantive arguments. However, her account promises to vindicate reason’s ability (and right) to distinguish sound justifications from mere rationalizations.