This thesis attempts to discuss two metaphysical aspects that appear in Edvard Munch's art: monism and synaesthesia. These two topics have been previously discussed by other art historians and critics; however it is this writer's opinion that the concepts in themselves were not properly understood in the first place. This, in turn, influenced their interpretation within the context of Munch's work. Monism and synaesthesia have been considered here in connection with their metaphysical background. Therefore this thesis discusses the topics first of all from an art historical perspective, then from a philosophical point of view. A certain knowledge of neurology as well as of history of religions has also contributed to the elucidation of the themes here discussed. The reasons for Munch's concern with metaphysical topics have been acknowledged here as well. These reasons were both general as well as private. The Weltanschauung at the end of the nineteenth century had a definite predilection for metaphysics and Munch was certainly influenced by it. In addition, he had very clear personal reasons to be concerned with such topics: death in his family as well as death threatening him in his childhood were serious grounds that were conducive to Munch's interest in metaphysics and therefore, in monism and synaesthesia.