Zum Außenweltproblem in der Antike: Sextus' Destruktion des Repräsentationalismus und die skeptische Begründung des Idealismus bei Plotin

Miles Burnyeat famously argued that there could, in principle, be no idealism in Greek philosophy, because it was not yet prepared to regard the existence of an external world beyond our veil of perception as a serious philosophical problem. I believe that this thesis is historically and systematically false. Burnyeat’s claim is backed up by a short sketch of the most important philosophical systems in Greek philosophy that might seem to contradict his no-idealism view, viz. ancient skepticism and Neo-Platonism. In this paper, I argue against Burnyeat’s view on the basis of a reconstruction of Sextus Empiricus’ epistemological skepticism regarding the external world. Then, I try to show that Plotinus’ idealism and his theory of νοῦς are built on the assumption that metaphysical realism entails the problem of the external world and is, therefore, potentially inconsistent because of its skeptical results. Plotinus shows how skepticism about the external world can be avoided by idealism which can, thus, be seen as an explicit overcoming of epistemological skepticism. This whole train of thought explicitly refers to the problem of an external world. Therefore, Plotinus can be seen as answering the skeptical challenge with an idealistic metaphysic of experience.