In tbis splendid collection of the articles and addresses of P. L. Kapitza, the author remarks on the insight of the 18th century Ukrainian philosopher Skovoroda who wrote: "We must be grateful to God that He created the world in such a way that everytbing simple is true, and everything compli­ cated is untrue. " At another place, Kapitza meditates on the roles played by instinct, imagination, audacity, experiment, and hard work in the develop­ ment of science, and for a moment seems to despair at understanding the dogged arguments of great scientists: "Einstein loved to refer to God when there was no more sensible argument!" With Academician Kapitza, there are reasoned arguments, plausible alter­ natives, humor and humane discipline, energy and patience, a skill for the practical, and transcendent clarity about what is at issue in theoretical practice as in engineering necessities. Kapitza has been physicist, engineer, research manager, teacher, humanist, and tbis book demonstrates that he is a wise interpreter of historical, philosophical, and social realities. He is also, in C. P. Snow's words, strong, brave, and good (Variety of Men, N. Y. 1966, p. 19). In this preface, we shall point to themes from Kapitza's interpretations of science and life. On scientific work. Good work is never done with someone else's hands. The separation of theory from experience, from experimental work, and from practice, above all harms theory itself.