This paper explores the influence of the fifth-century Christian Neoplatonist Pseudo-Dionysius the Areopagite (Denys) on the twentieth-century philosopher of science Paul Feyerabend. I argue that the later Feyerabend took from Denys a metaphysical claim—the ‘doctrine of ineffability’—intended to support epistemic pluralism. The paper has five parts. Part one introduces Denys and Feyerabend’s common epistemological concern to deny the possibility of human knowledge of ultimate reality. Part two examines Denys’ arguments for the ‘ineffability’ of God as presented in On the Divine (...) Names . Part three then explores how Feyerabend imported Denys’ account of divine ineffability into his own metaphysics to provide a novel argument for epistemic pluralism. Part four explains the significance of an appreciation of Dionyius’ influence for our understanding of Feyerabend. I conclude that Denys was a significant and neglected influence upon the later Feyerabend. (shrink)