Christ the Light: The Theology of Light and Illumination in Thomas Aquinas by David L. Whidden III (review)

David Whidden's purpose in this revised dissertation is to show how pervasive the language of light and illumination is in the theology of Thomas Aquinas. The analogy of light is very important for Aquinas, because it reveals something about God. Whidden notes that sustained investigations of Aquinas's use of light have been neglected in the past both because of the presumption that Aquinas was critical of divine illumination theories and therefore had less interesting things to say about illumination and because of Aquinas's rejection of thirteenth-century light metaphysics. At least partially as a response to those convictions, the book articulates three basic theses. First, for Aquinas, illumination "is the manifestation of truth with reference to God, who illumines every intellect" (7, quoting STh I, q. 106, a. 3; and q. 107, a. 2). Second, there are three kinds of illumination, the last two of which many scholars have ignored: the light of nature, the light of faith or grace, and the light of glory. Third, the illumination of rational intellects "is primarily the mission of the Son" (8). The literary structure of the book follows the general structure of the Summa theologiae, with chapter 2 (of seven) acting as an excursus on the differences between medieval and modern understandings of light. Throughout the book, Whidden is concerned to have particularly Christological dimensions of light woven into each chapter.

Whidden finds that a good place to begin an investigation into Aquinas's theology of light is the principium named Rigans montes. This work shows Aquinas's interest in light and illumination, and Whidden determines that Augustinian language about light seems to be just as influential on Aquinas as Dionysian language, at least in this work. Drawing on the Summa theologiae and several of Aquinas's scriptural commentaries, Whidden demonstrates that for Aquinas, Scripture and Tradition mediate light, and sacra doctrina, as a scientia, involves illumination as well. Sacra doctrina ultimately derives "from the Father of lights, who is the principal teacher of all of us, primarily through the visible and invisible missions of his Son" (46). Whidden argues that Christ is light, and while Christ illumines through his teaching and grace, "the focal point of Christ's teaching and illumination is found on the cross" (44). To counter the three natural darknesses of sin, ignorance, and condemnation, God, through Christ, has given the three lights of nature, grace, and glory, which are really the multiple effects of the one divine light.

Chapter 2 investigates the physics of light as it was understood in the Middle Ages. Following Aristotle, Aquinas says that light "is the actuality of the diaphanous considered as diaphanous" (II De anima, as quoted on 49). Humans are unable to see the colors of objects, which inhere in the surfaces of objects, unless light illumines a transparent medium (usually air or water) between the object and the eye (which also contains a medium of water). Against the position of Democritus, Aquinas argues that light is not a body, and against the position of Augustine and Bonaventure, Aquinas maintains that light does not have a spiritual nature. Neither is light "just the 'evidence of color'" (52, quoting II De anima), nor is lux a substantial form (the position of Robert Grosseteste and Bonaventure); lux is "the active quality of a heavenly body on the basis of which it acts" (II De anima, as quoted on 53). Important for later metaphysical considerations, Whidden notes that, for Aquinas, "light … does not have a contrary that resists its form" (54). Regarding human sight, Aquinas rejected Plato's theory of extramission and adopted Aristotle's view of intromission. Whidden highlights the fact that in the Summa theologiae, Aquinas adopts Aristotle's theory and develops his own arguments in favor of intromission, "which is a more passive process" than extramission (67), since in...