Coming Down From the Castle : LEWIS MUMFORD A Life <i> by Donald L. Miller (Weidenfeld & Nicolson: $24.95; 590 pp.</i> , <i> illustrated; 1-55584-244-5) </i>

The first question must be whether this book was necessary. Did not Lewis Mumford write his own inimitable biography? True, his “Sketches From Life” (1982) was a first volume that took us only to the mid-1930s, less than half-way through his 93 years. And, though Mumford lives on, his great pen is now sadly and permanently down.

But fully two-thirds of Donald L. Miller’s new biography covers the same ground. Indeed, the author--a historian from Lafayette College--takes half his text to cover Mumford’s fruitless and frustrating first quarter-century: the illegitimate birth to a Jewish businessman and a superficial, fun-loving mother; the dropping-out of school; the years of rejection slips. So, inevitably, there is much treading over old ground.

What then is new? First, Mumford’s life after 40, which marked an abrupt shift of direction with his entry into active political controversy. As Miller makes clear, until the mid-1930s Mumford was a remarkably unpolitical animal: In his first book, “The Story of Utopias” (1922), he thought the subject unimportant. “Our most important task at the present moment,” he then argued, “is to build castles in the air.”

The Nazis changed all that, making Mumford a passionate anti-isolationist; after losing his son to World War II, he came to believe that he had betrayed the whole of the younger generation. His critique of totalitarianism then extended into a passionate attack on the whole apparatus of technological power: It culminated in the campaign against Vietnam, for which he is best known among those under 40.

But in a way that was both curious yet absolutely typical of him; he never really changed the views he had formed as a young man. From start to end of his thought, he believed in the primacy of mind over matter: the capacity of the individual to shape the course of technological change for good or ill. Man, for him, was both a super-rational and a deeply irrational being: It was the supreme achievement of cultural history that it could draw attention to the demonic side of human existence and so help conquer it.

Miller shows that this was a central theme of one of Mumford’s later exercises in polemic, “The Myth of the Machine” (1964); but it had been the key insight of his study of Melville’s fiction 35 years earlier. It gives Mumford’s work a remarkable constancy, rather like the playing out of new and more complex variations on the same musical themes. But it does explain his failure ever to arrive at a convincing theory of political action.

That, Miller argues--and surely most readers will agree--is the anti-climactic disappointment of perhaps his greatest book, “The Culture of Cities” (1938). And his dear friend Catherine Bauer criticized its successor, “The Condition of Man” (1944): He was always seeking a messiah, she said, to begin some spiritual transformation. It was a comment so on-target that it stung Mumford to vehement response. Significantly, after laboring long to rewrite “The Culture of Cities,” he made it into “The City in History” (1961), leaving out the prescriptive part.

All this is new, fresh, relevant and full of insight. There is more in Miller’s book that is also new but is more questionable. Though he stresses that this is not an official biography, he has secured Mumford’s permission to use the secret archives at the University of Pennsylvania which Mumford himself declined to open for his autobiography; he has similarly had family permission to use Catherine Bauer’s private letters to Mumford.

That Mumford and Bauer were lovers after his marriage to Sophia Wittenberg was common knowledge to many long ago, since Mumford’s own autobiography is open to all who may read. But Miller now gives us the most intimate details of their relationship. There is a question of taste as to whether this should have been done while both he and Sophia live; there is another, as to what it tells us that we need to know.

True, Mumford carefully filed the letters and once told Bauer that they were cooking up a marvelous correspondence for posterity. (He was incapable, Miller suggests, of truly feeling anything unless he had written it all down.) He was hugely guilty of a double standard of morality for himself and for Sophia; he wanted Sophia the devoted wife, mother, secretary and proof-corrector, but he also needed Catherine the passionate intellectual, and he made sure he told both of them all about the other. He made love to Catherine on Manhattan afternoons, but always left precisely at 5 for supper with Sophia.

He was also culpable of egocentric self-dramatization, though perhaps--his career path then soaring--he had excuse. He was mortified when Catherine told him she had another lover, but she knew him better than he knew himself. She left him to work on a Philadelphia housing project and to have an affair with its architect, and he resented both. It was effectively the end, and he went on to another affair--never before detailed--with Alice Decker, Bauer’s closest friend.

Catherine Bauer, that great mother of the American public housing movement, is now long gone; Mumford himself is quiescent, and Sophia, we must suppose, content that all be known. But some things, including biographies themselves, are perhaps best left until they can give no hurt to their subjects. This book could decently have waited a while.