October 2007 Newsletter Vol. 36 No. 4
2007 Guggenheim Winners
A. Mark Smith is Curators’ Professor of History at the University of Missouri, Columbia. He has spent the last twenty-odd years working on a critical edition of Alhacen’s De aspectibus and is nearing the end of that project.
The purpose of this fellowship is to allow me a year’s research leave to begin work on the last phase of a long-term project to critically edit Alhacen’s De aspectibus, the medieval Latin version of Ibn al-Haytham’s Kitab al-Manazir. Consisting of seven books, the De aspectibus (“On Visual Appearances”) is subdivided into three main topical segments: the first dealing with the physical, physiological, and psychological grounds of visual perception (books 1-3), the second with the formation, perception, and misperception of mirror images (books 4-6), and the last with perception and misperception in refracting media. It is this last topical segment that I’ll be dealing with during the upcoming academic year.
Thanks primarily to David Lindberg, most of us are aware that Alhacen’s De aspectibus was the key source for the study of optics between the mid-thirteenth and early seventeenth century, when Kepler transformed that study with his theory of retinal imaging. Friedrich Risner took a major step in this transformation with the publication in 1572 of his Opticae Thesaurus, which included the edito princeps of Alhacen’s treatise.
Risner’s edition was crucially significant because it made the De aspectibus far more accessible than it had been. This it did in two ways. First, and most obvious, it made more copies available to a wider audience than was possible in manuscript form. Second, by importing certain key editorial changes, Risner made it more easily readable. Not only did he publish it in a clear Roman font with few abbreviations, but he broke it into digestible theorematic chunks, adding his own enunciations to forewarn the reader about what was to be demonstrated in each of those chunks.
As a result, Risner made the De aspectibus easier to assimilate, but he also made it easier to read selectively according to specific topics. Why, after all, slog through the entire treatise when your sole concern is the analysis of concave spherical mirrors? Why not focus on those, and only those propositions dealing with that subject? And why not let the enunciations guide you to those propositions that seem particularly relevant to your specific interest?
The problem with this piecemeal approach, which has determined how the De aspectibus has been read and interpreted since the late sixteenth century, is that it traduces Alhacen’s original intent in writing the treatise. He meant it to be read as an extended essay bound together from beginning to end by a complex web of logical interconnections. To read it selectively according to particular topical or theorematic segments is to break that web and, along with it, the all-important systematic links that bind the treatise into an extraordinarily elegant whole.
That, in a nutshell, is why I’ve devoted most of my career to editing the De aspectibus from the manuscripts: to restore it, insofar as feasible, to the form in which it was actually read during the Middle Ages and Renaissance. Rereading the De aspectibus in that form will, I think, force some subtle but significant revisions in the current understanding of Alhacen’s role in the development of Keplerian and post-Keplerian optics.