It is now considered established that modern epistemology has discovered the problem of solipsism. In contrast, ancient philosophy, starting from a "healthy" realism, never questioned the existence of a non-mental external world. This view is incorrect, as Markus Gabriel demonstrates in his original study. His thesis is that ancient skepticism has thought through the problem of the external world in a far more radical way than the Early Modern period. Through the skeptical anti-philosophy of Sextus Empiricus and Plotinus' idealistic metaphysics, as well as against the backdrop of contemporary philosophy, he makes it clear that ancient skepticism presents a way of life that leads out of the paradoxes of contemporary epistemology.