This work had its origins in my accidental acquaintance in 1987 with a number of J.M. Keynes's early Apostles papers. Because of this, my introduction to Keynes's philosophical thinking was not through the Treatise on Probability, but rather the unpublished papers Keynes wrote in the years before he began the Treatise. In contrast, most scholars interested in Keynes and philosophy seem to have gone directly to the Treatise, Keynes's major philosophical work. This meant that they began with a work that had been polished for publication over many years, and from which Keynes's hesitations and second thoughts had been either eliminated or finessed. The early Apostles papers, on the other hand, show Keynes thinking on his feet, exploring ideas openly, without concern for publication. They immediately suggested a process of early intellectual development in which Keynes entertained his first theoretical commitments and considered their costs. In my view, this more candid Keynes needs to be closer to the center of our image of Keynes and philosophy, both because Keynes himself was accomplished at placing the weak points in an argument in the background when he turned to the public, and because philosophy itself inescapably involves a balancing of competing considerations that leaves every defended position conditional upon questions and principles put aside. To begin with Keynes's Apostles papers, then, made Keynes an essentially dynamic thinker, one constantly adapting his views as he engaged issues, rather than one producing definitive works later to be labeled classics.