EXCERPT A metaphor for understanding the complex transits that take place in contemporary mathematics can be found in the image of an articulated pendulum. Unlike a simple pendulum, which, as it sweeps its course, determines a fixed frontier, equidistant between its extremes, an articulated pendulum—built by linking together two pendula oscillating in opposite directions—defines an altogether extraordinary dynamic curvature, unimaginable if one were just to consider the two pendula separately…