Formal approaches are very influential in philosophy with many successes in logic, formal epistemology, semantics, and normative decision theory. Past philosophical formal developments have been influential outside of philosophy in areas as diverse as computing, linguistics, and economics. Formal approaches are understood and promoted as instances of scientific philosophy. Like all methods, formal approaches have systematic benefits and costs, global strengths and weaknesses. Practitioners of formal philosophy have articulated cogent accounts of the ongoing promise of their methods. By contrast, potential limitations, abuses of formal methods, and indirect harms have been relatively neglected. In this project we explore the arguments against formal approaches in philosophy in historical and systematic context. On the historical side, this project aims to recover now largely forgotten debates over the merits of formal techniques in philosophy in the 18th century, roughly, the period between Kant and Newton. While 'philosophy' had a broader signification then, several of the arguments are still significant for today's debates over the methods of philosophy (so-called eta-philosophy). On the systematic side: the great attraction of formal approaches is their topic neutrality. Yet, topic neutrality entails that many substantive issues are extrinsic to formal methods. The implication of this may be that formal methods need to be supplemented in non-trivial fashion.