Austin, Texas — Laurance S. Rockefeller, the tall, elderly Rockefeller brother known to be a philanthropist and a conservationist, was about to sit down to a conference lunch of brisket and sausage on the eighth floor of the Lyndon Baines Johnson Library here.
He was wondering aloud what he would say the next day when his turn came to speak at a national gathering of architects, city planners, and others at a conference on future design of American cities and the environment.
''If we don't have some kind of goal beyond ourselves, how are we going to have a high quality of life?'' he asked. ''If you're going to have quality of life, you've got to have a renewal of the spirit.''
That was the phrase he wanted, he said - ''a renewal of the spirit.'' He asked someone standing next to him to write the phrase down, then he took the piece of paper and pushed it into his suit coat pocket.
The next day, when his turn came, Mr. Rockefeller spoke of paying greater attention to ''the moral and spiritual resources and quality of the human spirit.''
It was a theme repeated by the other experts as they debated how to better shape American cities and better respect the environment.
There was little agreement over the specifics of whether, for example, to limit the height of buildings - something San Francisco and the District of Columbia do, as former Interior Secretary Stewart L. Udall noted. A proposed development in Philadelphia would tower 200 feet over the hat on the statue of William Penn that stands atop the City Hall tower, now the tallest structure in the city. The development proposal has stirred considerable controversy.
Nor was there much agreement about whether modernistic buildings were preferable to preserved and renovated ones.
Robert A.M. Stern, an architect and professor at Columbia University, warns against ''hysterical preservation'' - the effort of trying to save all old buildings.
But, he adds, ''young people are fed up'' with much of today's development in cities. ''They've driven up and down the strip one too many times.'' Too often, there is ''an absence of any vision'' in urban development today.
Lady Bird Johnson, the wife of the late President and a major force behind the conference, challenged the experts here by defining ''social consciousness for an architect'' as ''planning and building which respects the Earth's green mantle, clean air, clear waters, open spaces, and the wilderness.''
Architect Nathaniel A. Owings of Skidmore, Owings & Merrill quickly accepted the challenge. ''Intellect is what kills that marvelous thing called instinct,'' he said. ''Most of my good ideas have been killed by someone thinking it through and saying it can't work.''
He proposes limiting new city structures to 22 stories. Time magazine design critic Wolf Von Eckardt suggests that those who want to build beyond height and depth limitations should pay extra to the city.
To architect Stern, all tall buildings aren't detractions. And many one-story buildings are ''bad,'' he says.
Mr. Owings admits his own company has designed many of the kinds of modern, urban high rises he and others criticize, including some in Houston. Asked about this, he said the clients call the shots to a large degree.
Most major cities have at least a few of the glass-exterior, box-like high-rise office towers that have become increasingly common in recent years. Owings calls them monuments to ''ego.''
Houston architect Robert H. Timme calls his city ''a giant corporation chessboard - the pieces on the chessboard are the corporation towers.''
New York Mayor Edward Koch, among others, says it's not the buildings but the people who make a city. As could be expected, he states: ''The city of New York is the most exciting city in the world; and it comes from the diversity of its people.''