The idea behind this session of the summer school will be to explore how the concept of Friktion, in its connection to the philosophical notion of actuality (Wirklichkeit), is at work in the philosophy of German theorist of war Carl von Clausewitz (1810–1831). It will explore how Friktion, similar to experience for Immanuel Kant, functions as a critical touchstone for Clausewitz. The session will, therefore, explore the physical and philosophical concept of Friktion in its relation to actuality from within a post-Kantian framework, asking why it became so important for Clausewitz’s own critical philosophy of war.