Herman Kahn, a physicist who has been a consultant to the Department of Defense, the Office of Civil and Defense Mobilization, and the Atomic Energy Commission -- presently director of the Hudson Institute -- has put together a ""guide to clearer thinking about the military and political realities of the days ahead"" which may very well change any number of intellectual, honest minds committed within the peripheral areas of Sane Nuclear Policy thinking. ""In our times"", Kahn warns, ""thermonuclear war may seem unthinkable, immoral, insane, hideous, or highly unlikely, but it is not impossible."" And throughout he works with possibility --extrapolating, theorizing, second-guessing, analogizing, psychologizing, philosophizing and, from time to time, apologizing -- insisting, however, that ""we may do this inadequately and thus be misled, but we are likely to be misled more grossly if we do not try."" He discusses deterrence, the arms race, disarmament, the possibility of accidental war, war by miscalculation and catalytic war. His lucid, thoughtful, and knowledgeable treatment of civil defense - - it is this chapter which will most likely win the uncommitted and sway the committed -- is the most convincing argument for an enlightened civilian shelter program that this reviewer has read to date. Although Kahn is aware of every antithesis, of every ""yes-but"" of counter opinion, his necessary straw-men are erected with respect, tolerance, and accuracy. Herman Kahn is an eminently sensitive, remarkably convincing writer. He's accomplished what few approach. The advance blurbs seem justified.