Which Reasons? Which Rationality?

The slogan that rationality is about responding to reasons has a turbulent history: once taken for granted; then widely rejected; now enjoying a resurgence. The slogan is made harder to assess by an ever-increasing plethora of distinctions pertaining to reasons and rationality. Here we are occupied with two such distinctions: that between subjective and objective reasons, and that between structural rationality (a.k.a. coherence) and substantive rationality (a.k.a. reasonableness). Our paper has two main aims. The first is to defend dualism about rationality – the view that affirms a deep distinction between structural and substantive rationality – against its monistic competitors. The second aim is to answer the question: with the two distinctions drawn, what becomes of the slogan that rationality is about responding to reasons? We’ll argue that structural rationality cannot be identified with responsiveness to any kind of reasons. As for substantive rationality, we join others in thinking that the most promising reasons-responsiveness account of substantive rationality will involve an “evidence-relative” understanding of reasons. But we also pose a challenge for making this idea precise – a challenge that ultimately calls into question the fundamentality of the notion of a reason even with respect to the analysis of substantive rationality.