This chapter explores the uses and perception of light in religious architecture. Often characterized as an ambiguous materiality—neither concrete and tangible nor distinctly immaterial—light seems to offer itself readily as both matter and metaphor for the divine. We argue in this chapter that this is precisely what happens in contemporary Danish churches, yet not without conflicts between the ideal of immaterial divinity and the need for tangible religious practices. We trace a number of luminous as well as numinous qualities to medieval church architecture, still in use today, and show that despite architectural continuities, modernist churches capture and cherish light in a number of ways that emphasize mainly its immaterial aspects. Architectonic discourse is seen as challenged by light practices in the churches, where light lends itself as an instrument for bridging the ontological positions of matter and spirit.