This book explores the idea that there is a certain performativity of thought connecting Kant's Critique of Pure Reason and Wittgenstein's Tractatus Logico-Philosophicus. On this view, we make judgments and use propositions because we presuppose that our thinking is about something, and that our propositions have sense. Kant's requirement of an a priori connection between intuitions and concepts is akin to Wittgenstein's idea of the general propositional form as sharing a form with the world. Aloisia Moser argues that Kant speaks about acts of the mind, not about static categories. Furthermore, she elucidates the Tractatus' logical form as a projection method that turns into a so-called 'zero method', whereby propositions are merely the scaffolding of the world. In so doing, Moser connects Kantian reflective judgment to Wittgensteinian rule-following. She thereby presents an account of performativity centering neither on theories nor methods, but on the application enacting them in the first place.