'Cambridge University Press are to be congratulated on making these two excellent and thought provoking lectures available. Elementary Particles and the Laws of Physics is a book that all physicists will be pleased to have on their shelves, and one that will surely stimulate aspiring theoretical physicists.' Tony Hey, New Scientist 'Richard Feyman and Steven Weinberg are both outstanding lecturers and expositions. All those interested in the development of modern physics will find this a fascinating book.' Physics Briefs 'Most enjoyable and stimulating reading; highly recommended.' A. G. Klein, Australian Physicist 'Recommended reading for anyone interested in Dirac's work.' B. R. Parker, Choice 'The text of the 1986 Dirac Memorial Lectures, long available as a slim hardback, is now available in paperback. Over a decade later, the messages in these lectures remain fresh.' International Journal of High-Energy Physics '... readers of this booklet will not be disappointed.' Hubert Goenner, General Relativity and Gravitation