Burt C. Hopkins, The Origin of the Logic of Symbolic Mathematics: Edmund Husserl and Jacob Klein is reviewed at NDPR. Just as I was finishing my PhD, and was getting interested in questions around calculation, my friend Morris Kaplan suggested I read two books. One was Klein’s Greek Mathematical Thought and the Origin of Algebra; the other was David Lachterman’s The Ethics of Geometry: A Genealogy of Modernity. Klein was a student of Heidegger’s, part of the group that took his early 20s classes on Aristotle and Plato. Lachterman was a student of Klein’s. Both books were incredibly useful to me, and I doubt I would have written Speaking Against Number without their influence. Both also helped shape parts of the argument of The Birth of Territory. I  didn’t know about the Hopkins book, but it looks very interesting.