Wednesday 26th June provided another intense day for discussion and reading. The morning session of the conference featured papers by Cecilia Panti, Neil Lewis and Brian Tanner, chaired by Pietro Rossi. Cecilia presented a detailed exposition of Grosseteste’s use of mathematical sequences within the De luce, especially in its first half. The infinite multiplication of form (light) within matter is a key concern here, and Grosseteste may have been responding to an articulation by Averroes of the difficulties inherent in expressing infinite multiplication. The fourfold notion of form, matter, composition and the composite would come up again in the afternoon discussion, but Cecilia’s discussion served to underline again the place of mathematical reasoning within the treatise. She also reminded us of the provisional nature of the De luce, and that it should not be thought of as Grosseteste’s final word on the central issues of body, form matter and being. Neil Lewis took us on a different journey, through Grosseteste’s use of light in the commentary on Aristotle’s Physics, for the nuances and complexities of the nature of substance, how substantial body is to be described, how unity and diversity are to be accounted for, and issues of potentiality and actuality. Neil underlined the importance of light as ‘the first corporeal form’ as high in the order of Grosseteste’s contributions to the history of ideas (with some early hints in Avincenna, but not in anything like the operative use the De luce achieves). Brian then explored the axioms that may be detected in Grosseteste, and his own
engagement with the text as a modern physicist. The fact that Grosseteste identified physical ‘laws’ and arrived at conclusions through logical thought was striking, as the notion too that unity runs through the structure of the treatise and the universe it envisions: below or above the sphere of the moon the universe is still composed of the same ‘stuff’. Brian drew attention here to the notion of phase transition – ice cream turning to liquid, but still the same ‘stuff’ (an analogy that became popular given the high temperatures in Porto). The place of symmetry in both Grosseteste’s universe and in modern scientific explanation provided a perfect place to conclude the sessions.
After that, the afternoon session took a more traditional ‘ordered universe’ form. The whole group sat round together, and we went through the first half of the De luce, line by line, and in some cases word by word. The experience is a fresh one each time, and every time I forget just how enriching it is, and how hard you have to 
concentrate! The afternoon was no exception, with discussion over particular translation, how particular sections of the treatise lock together, sections which remain difficult to interpret, and how the expanding universe followed by the inward expansion of lumen to perfect the celestial spheres, and the imperfect region below the moon. I was once more struck by the majestic quality of Grosseteste’s imagination, and the questing nature of his explanation of the problems he both set himself, and with which he found himself confronted. The metaphysical tone of the treatise, in some comparison to the De colore or the De iride, was something I at least encountered more forcefully than before. After more than two hours hard concentrating, it was time for a rest…with more to come the next day: principally the education strand of the project…
p.s. this was our most visited day on the blog. Thanks for reading! Giles
Mike and Sam relaxing…