The goal of this article is to explain how the concept of Illumination came to be a source of skepticism in the modern West. In ancient and medieval Christian thought it was essentially tied not only to Plato’s philosophy, but especially to Augustine’s invention of the notion that the soul is an inner chamber containing all his knowledge, but also the locus of his encounter with God. The concept of the soul or mind as an inner chamber re-emerged in early modern western philosophy, but it was no longer open to illumination, John Locke having made revelation into an entirely distinct category of knowledge. The set of ocular metaphors of which illumination is a part still has an important place in ordinary language, but can no longer provide for a philosophical theory of knowledge. Thus, different complex metaphors need to be employed. Alasdair MacIntyre’s account of human reason begins with social practices, and can be described as an extensive thesis reflecting the metaphor Knowing as Doing. With his incorporation of Thomas Aquinas into his account of tradition-constituted rationality, it is suggested that interesting parallels might be found with the work of Mulla Sadra.