According to the new investigators of adult development, that disquieting ""midlife crisis"" may precipitate a vocational soul-searching and the assumption of a new persona. Professor Krantz, considering a radical change in his own career, went to the laboratory hothouse of Santa Fe. There he met and interviewed a dozen luftmenschen--those who seemingly subsist on air and on contemplation. Self-exiled from difficult relationships and regular paychecks, they are predictably and unabashedly serf-indulgent. Once the direction of any life is examined, they unanimously believe, the need for an altered course will be evident. Former colleagues are faulted for not making similar re-evaluations and reformations. Certainly, many other white-collar workers and professionals may eventually find that the rewards are not worth the game. But Krantz is weak in analogizing from specifics to larger matters, and his advice is murky. Though he suggests that frames of reference are necessary to find one's own identity, solutions matter less to him than articulating the problems. Some earnest introspection, little practical assistance.