This first full-length biography of Paul Adrien Maurice Dirac offers a comprehensive account of his physics in its historical context, including less known areas such as cosmology and classical electron theory. It is based extensively on unpublished sources, including Dirac's correspondence with Bohr, Heisenberg, Pauli, Schr dinger, Gamow and others. Dirac was undoubtedly one of the most brilliant and influential physicists of the twentieth century. Between 1925 and 1934, the Nobel Prize laureate revolutionized physics with his brilliant contributions to quantum theory. This work examines Dirac's successes and failures, and pays particular attention to his opposition to modern quantum electrodynamics; an opposition based on aesthetic objections.