MIES VAN DER ROHE; A Critical Biography. By Franz Schulze. University of Chicago Press. 355 pp. $39.95; MIES VAN DER ROHE; The Villas and Country Houses. By Wolf Tegethoff. Museum of Modern Art. 223 pp. $55.

IN 1947 Philip Johnson's grounds for writing a study of Mies van der Rohe were that, as he later put it, "I just wanted to show that Mies was the greatest architect in the world." In Peter Blake's The Master Builders, which was published in 1960, Mies was given heroic status as one of the "three great lawgivers" of modern architecture. The subtitle of Franz Schulze's readable, well-researched and sympathetic biography underlines the fact that this kind of approach has become virtually impossible. Even his admirers now admit that there is plenty in Mies to criticize.

Schulze's criticisms of Mies' buildings are gently put, but they often appear to be euphemisms for "uninhabitable" or "unworkable." In his glass-sheathed Lake Shore Drive Apartments, "the clear glass is beautiful, but on account of its single thickness it offers relatively little resistance to shifts of heat or cold." The present owner of the Farnsworth House is described as an occasional visitor who "derives sufficient spiritual sustenance from the reductivist beauty of the place to endure its creature discomforts." The monumental main hall of the Berlin National Gallery "has remained by consensus an inhospitable arena in which to display any but the largest objects." Mies himself is quoted on this. "It is such a huge hall . . . that of course it means great difficulties for the exhibiting of art. I am fully aware of that. But it has such potential that I simply cannot take these difficulties into account."

These are appalling remarks for an architect to make, and it is as an artist, not as a practical or functional (whatever that may mean) designer that Mies is defended today: one can sense the pleasure with which Schulze turns to his Barcelona Pavilion, "an assignment so free of practical limitations that he could make pure architecture of it." And as an artist nothing is ever going to reduce his formidable status. His technology was not especially adventurous or advanced as technology: steel-frame construction had already become a way of life in Chicago by the time he got there in the late 1930s, and in 1898 the Tietze Store in Berlin used curtain walling made up of huge sheets of glass more daringly than Mies was ever to use it. It was his design which was revolutionary. Mies' towers, regardless of their practical advantages or disadvantages, are breathtakingly beautiful objects; and familiarity should never allow one to forget the explosive power of the phrase "less is more" as a summary of the esthetic philosophy behind them. His pavilions and houses played with space in a way in which it had never been played with before, and used walls of glass to establish completely new kinds of relationships between inside and outside. His own drawings suggested those relationships with an economy of line that can be as dazzling, in its own way, as the buildings themselves. They can be studied with pleasure in Wolf Tegethoff's monograph, along with analyses of individual designs which are sometimes as exhausting as they are exhaustive.

Schulze discusses Mies' beliefs at length. He read philosophy with great seriousness. He believed devoutly in the "spirit of the age" and in Thomist distinctions between essence and accident. He set out to design buildings which were "true" because they expressed the spirit of the age and the essence of the materials employed in them. Intellectually his philosophy was not impressive, but it was important because he believed in it, and it gave intense conviction and concentration to his work as a result. He saw his buildings not just as possible ways of dealing with situations but as the only ways, and his many admirers and disciples took him at his own valuation. "Do you ask God,"as Philip Johnson put it, "where He got His Commandments?"

TODAY this all seems disastrous because of the appalling cumulative impact of the Mies-type buildings designed with none of his flair all over the world. His admirers are now eager to distinguish between the quality of genuine Mies and the lack of quality of his imitators. But one cannot write off his responsibility so easily. The great Gothic cathedrals which Mies so much admired were based on a way of building which could be adapted by provincial masons for modest parish churches with pleasing results. It may be dangerous to draw comparisons between a man's private life and his public works, but it is tempting to do so in Mies' case. He was a powerful character who could inspire great devotion, but his life was as reductivist as his architecture -- occupied by drink, sex, cigars, St. Thomas Aquinas, his own buildings, and remarkably little else. It was not a basis from which to build humane buildings.