The years covered by this volume of the Collected Papers of Bertrand Russell were among the most productive, philosophically speaking, of Russell's entire career. In addition to the papers reprinted here, he bought Principia Mathematica to its finished form and wrote The Problems of Philosophy, Theory of Knowledge and Knowledge of the External World. In October 1910 he began teaching at Cambridge, having accepted an appointment as lecturer in logic and the principles of mathematics at Trinity College for a term of five years. A year later Ludwig Wittgenstein began to attend his lectures. Within a few months he was influencing Russell's philosophical thinking as much as, or more than, Russell was influencing his.