 Even with the publication of its three volumes, Principia Mathematica was incomplete. For example, the logical reconstruction of the various branches of geometry still needed to be completed and published. In fact, it was Whitehead’s task to do so by producing a fourth Principia Mathematica volume. However, this volume never saw the light of day. What Whitehead did publish were his repeated attempts to logically reconstruct the geometry of space and time, hence extending the logicism project from pure mathematics to applied mathematics or, put differently, from mathematics to physics—an extension which Russell greeted with enthusiasm and saw as an important step in the deployment of his new philosophical method of logical analysis.