This study investigates the concept of light in the early Jewish-Christian exegesis of the biblical creation narrative (Gen. 1, so-called ‘hexaemeron’). The study argues that the early hexaemeral exegetes theorised light from a dual perspective, both physical and metaphysical. The physical exegesis explained how light emerges as the natural capacity or power of the first material element of the world: fire. The metaphysical exegesis aimed to capture that light is the first immanent form of creation. The argument evolves in three stages. The first chapter discusses contemporary objections to the possibility of an investigation into the nature of light in ancient sources. It argues for the coherence of an ancient ‘physics of light,’ properly speaking, that was also used by hexaemeral authors in the course of their scriptural exegesis. The second chapter addresses modern and ancient objections to the justifiability of a scientific reading of Scripture. It aims to show that in the eyes of early Christian exegetes the rational enquiry into the physicality of light was indispensable for a proper understanding of the skopos (intended meaning) of the biblical creation narrative. Once the historiographical and hermeneutical objections have been removed, the study proceeds with the investigation of the nature of hexaemeral light itself. The third chapter proposes a systematic reconstruction of the hexaemeral theory of light, as it would appear at the end of the fourth century, taking into account its historical development from Philo to Ambrose, with Origen, Basil and Nyssen as the main protagonists. It shows that, from a premodern perspective, the rational account of the nature of light leads through the study of the physical properties to the grasp of the logos or intelligible cause of light. The three chapters build gradually towards the insight that the logos of light is the first manifestation of the logos of God in creation.

The study offers a performative argument that, in the eyes of early hexaemeral exegetes, the metaphysics of creation is inherently incarnational: the contemplation of the light of the world reveals Christ as the creative logos of God at work. In this way, the study points towards a Christological answer to the much-debated question whether the talk of God as light (socalled ‘metaphysics of light’) is literal, metaphorical or anagogical. It thus provides the necessary background to deciphering the precise meaning of the Nicene formula ‘light from light.’