The Theological Use of Science in Robert Grosseteste and Adam Marsh According to Roger Bacon: The Case Study of the Rainbow

In this paper, I deepen Roger Bacon’ s claim on the importance of science for theology for verifying how much it adheres to Grosseteste’ s view on the same subject. It is known, in fact, that in the works written for Pope Clement IV, Bacon asserts that his tenet is exemplified in the writings of Grosseteste and his friend and pupil friar Adam Marsh. Bacon indeed, presents himself as a representative of their tradition of teaching, as if their influence on him had been decisive in turning him to the interests associated with both scholars. The claims by Bacon concerning the use of philosophy and science for theology are here examined in their application to a relevant case study, namely the nature of the rainbow. In spite of Bacon’ s explicit assertion that Grosseteste’ s De iride  reveals that sciences are fundamental for theology, Bacon’ s distance from Grosseteste’ s view is definite and clear, not only with regard to the nature of the rainbow, but also its utility in the scientia divina. Hence, the only way for verifying Bacon’ s words, apart from testing their accordance with Grosseteste’ s claims, is to confirm the reliability of Bacon’ s direct acquaintance with both scholars. The first part of this paper deals with this question, while the second part examines Bacon’ s theory of the rainbow in its theological framework. In the third section, I consider the differences between his and Grosseteste’ s thought on the nature of the rainbow.