I was sorry to learn of the death of Professor Charles C. Gillispie (On the Campus, Nov. 11). In 1966, he was my preceptor in his “History of Science” course based on his seminal book, The Edge of Objectivity. I wrote a term paper in which I ascribed a certain scientific idea to Descartes. When the graded paper was returned, I saw that he had written in the margin next to that paragraph this succinct note in colored pen: “Not in Descartes.” I was floored. Of course he was right, but the enormity of those three words have stayed with me. My professor was sufficiently familiar with all the works of Descartes that he could tell me offhandedly that a particular idea did not appear in any of them! A few years ago, when he was 95, we had some correspondence, and he was as gracious and brilliant as always.