 In the latter parts of The Logic of Modern Physics Bridgman gave a fascinating array of discussions on the concepts of force, mass, energy, light and field, and the theories of thermodynamics, relativity and quantum mechanics. These thoughts were developed further in the remaining decades of his life, and collected in subsequent volumes including The Nature of Physical Theory (1936), The Nature of Thermodynamics (1941), Reflections of a Physicist (1950, second edition 1955), The Nature of Some of Our Physical Concepts (1952), and The Way Things Are (1959a). Bridgman made a searching examination of the familiar concepts of classical physics, checking to see if they retained operational meaning in domains of phenomena that were unfamiliar to the creators of classical physics. In some cases his analysis showed that the classical concepts were operationally unsound even in the contexts in which they were originally created. Later in life he stated that his initial foray into philosophy was motivated by his “disquietude” about physics, especially electrodynamics and thermodynamics, in which “the fundamental understanding of even the acknowledged leaders in physics were inadequate” (Bridgman 1959b, 519). In contrast, he thought that on the whole the contemporary development of quantum theory went in the right direction, especially in Werner Heisenberg’s version of it, which discarded classical concepts where they did not apply (e.g., space-time orbits for electrons), and crafted new concepts with clear operational meaning in new domains of phenomena. However, he was not entirely satisfied with Niels Bohr’s doctrine that all the operations of physics needed to be explained in the “macroscopic language of daily life or of present-day philosophy”; rather, he thought we needed to develop a “more adequate macroscopic language” (1959b, 526).