From astrophysics to condensed matter theory, nearly all of modern physics employs the path integral technique. In this presentation, the developer of path integrals and one of the best-known scientists of all time, Nobel Prize-winning physicist Richard P. Feynman, presents unique insights into this method and its applications. Avoiding dense, complicated descriptions, Feynman articulates his celebrated theory in a clear, concise manner, maintaining a perfect balance between mathematics and physics.brThis emended edition of the original 1965 publication corrects hundreds of typographical errors and recasts many equations for clearer comprehension. It retains the original's verve and spirit, and it is approved and endorsed by the Feynman family. The opening chapters explore the fundamental concepts of quantum mechanics and introduce path integrals. Subsequent chapters cover more advanced topics, including the perturbation method, quantum electrodynamics, and the relation of path integra