In Either/Or I, the aesthete, A, gives us the following diagnosis of his predicament: “I think I have the courage to doubt everything; I think I have the courage to fight everything. But I do not have the courage to know anything, nor to possess, to own anything.” In this chapter, I explore A’s fascinating claim that knowledge requires courage by way of juxtaposing the aesthetic life with Cartesian skeptical doubt. I show that just as the Cartesian doubter seeks refuge from radical skepticism in the safety of introspective knowledge – what is directly present to consciousness – so the aesthete seeks solace in the moment and what is sensuously present to him. Both methods ultimately prove ineffective and spurious, however: Cartesian introspection imprisons us in a mental cage with no beyond, just as aestheticism holds us captive in a self-spun world where our self dissolves. Consequently, what both the aesthete and the Cartesian need to do is to develop the strength to confront and overcome the anxieties that have motivated the flight from “the outer” (the flight from the world) in the first place.