Turning Points in Physics is a series of 1958 lectures presented at the Oxford University in Trinity Term. This six-chapter book highlights the interplay between assumptions, theories, and experimental discoveries in physics. The first chapter provides a brief introduction to the physical theory and field physics. The following two chapters cover the basic principles of quantum nature of matter and radiation, as well as the introduction of the probability concept in the field physics. The discussion then shifts to the theory of relativity and the fundamentals of cause and effect. The last chapter focuses on the concept of elementary particle physics. This chapter also explores general topics in physics, including conservation, quantization of change, fermions, bosons, mirror symmetry, gravitation, and masses. This book is directed toward physicists, theorists, and physics teachers and students.