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3 Light and Language While we now have a better understanding of the physics of light according to Aquinas, his theological use of light language varies. Just as we may misunderstand Aquinas’s theology by misunderstanding his physics, so too we run the same risk by misunderstanding the variety of purposes for which he applies light language. In this chapter we will discuss some of the basic light terms he uses, including the often important distinction between the two Latin terms for light, lux and lumen, and then explore the three main uses of light language in Aquinas, those of metaphor, analogy, and model. We will conclude with a discussion of how Christ fulfills our understanding of the language of light. Some Basic Light Terms One of the drawbacks to reading English translations of Aquinas is that English only has one word for light, while Latin has two, lux and lumen, which have technical meanings for Aquinas.1 In his commentary on Lombard’s Sentences, he describes lux as “that which is in a lucid body that is in act, by which others are illuminated, as in the sun,” while lumen is that which the diaphanous body receives for illumination.2 Robert Pasnau explains that lux “refers to being a source of light, whereas the latter [lumen] refers to the illumination emitted by that source.”3 When applied theologically, to say that God or Christ is lux is to 1. For a helpful history of the Neoplatonic roots of this distinction, see Yael Raizman-Kedar, “Plotinus’s Conception of Unity and Multiplicity as the Root to the Medieval Distinction Between Lux and Lumen,” Studies in History & Philosophy of Science Part A 37, no. 3 (2006): 379–97. Cf. James McEvoy, “The Metaphysics of Light in the Middle Ages,” Philosophical Studies 26 (1979): 126–45. 2. II Sent. 13.1.3. 3. Thomas Aquinas, A Commentary on Aristotle’s De Anima, 218, fn. 8. 69 say that they are the source of all light, and to say that the apostles have lumen is to say that they receive their illumination from another light source. Light rays (radii) are beams of illumination that travel in a straight line from their source, and are thus a species of lumen, while splendor (splendor, often translated as “glory”) is the reflection of light rays off of one body onto a third.4 The latter of these two terms is the more important, as Aquinas will often speak of Christ as the glory or splendor of God, suggesting that the Incarnation makes it possible for us to see God’s light reflected from his Son, though Aquinas also believes that Christ, as the Incarnate Son, is true lux. Finally, and perhaps more controversially, I would argue that the term “illumination” (illuminatio) has a different meaning than is usually acknowledged among students of Thomas. Often illumination is treated as if it applies to any form of cognition for Aquinas, most especially natural cognition. For instance, illumination is defined by Kevin Corrigan as “the natural activity of the agent intellect which lights up the essence of the sensible thing so that it becomes intelligible by the possible intellect”;5 Robert Pasnau describes illumination as the process “according to which human beings are illuminated by the ‘unchangeable light’ so as to attain the ‘eternal rules’”;6 and Matthew Cuddeback argues that illumination “brings to bear on our truth-knowing the authoritative rule (regula) of the First Truth.”7 Some of this is naturally the consequence of Aquinas’s use of the idea of the light of the agent intellect in our natural cognition. Since what lights do is illuminate, then our cognitive processes would seem to be a process of illumination, especially when Aquinas speaks of our natural light. Additionally, Aquinas is modulating the theory of illumination that he and his contemporaries inherited from the Augustinian tradition, which held that any kind of knowledge required divine illumination. So philosophers and theologians have quite naturally conflated illumination with cognition, most especially our natural cognition.8 Illumination, however, in its most proper sense is a light or manifestation of the truth that orders our knowledge to God. Aquinas discusses this with 4. II Sent. 13.1.3. 5. Kevin Corrigan, “Light and Metaphor in Plotinus and St. Thomas Aquinas,” Thomist 57 (1993): 198. 6. Robert Pasnau, “Henry of Ghent and the Twilight of Divine Illumination,” Review of Metaphysics 49, no. 1 (1995): 50. 7. Matthew Cuddeback, “Thomas Aquinas on Divine Illumination...

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