Steve Coll's Post Magazine article {June 10} gave a turn to a major land-use planning ferment in Montgomery County. As a stirrer of that ferment, I have been thinking ever since of his article and the letters {Magazine, July 22} responding to it.

No doubt the building industry and politicians dismissed his lament for the lost landmarks of his youth. Montgomery County has grown enormously; of course the small shopping centers of Bethesda and Rockville Pike would disappear. The only option would be to, shudder, stop growth. That is the easy answer. But if the county had worked harder, could it have made new development fit into the existing fabric, preserving, if not the exact shops Mr. Coll remembers, at least the visible manifestations of the community? Is his lament just sentimentality? Or did we lose something important when we lost what Jane Jacobs called "public life"?

One of the letters cited several groups that help the poor in Gaithersburg as foundations of the community. It startled me to think that we need the poor to give us a sense of community. The poor are of necessity public people. They need to walk and wait for buses. They tend to congregate in places that lend themselves to walking and meeting their friends.

Old Town Gaithersburg is one of the few such places in Montgomery County. You can -- and people do -- walk down Summit Avenue and speak to neighbors, city council members and street people. It is no accident that the soup kitchen is in Old Town, not Montgomery Village. There may be a few poor people in Montgomery Village, but no one sees them, no one knows them.

Without public life, there is no public morality. Contrast the outpouring of support for the soup kitchen (which has more than 400 volunteer workers) with the outpouring of self-interest from a subdivision-based civic association: A big banner was reported to decorate the wall at a forum for county council candidates, saying "What can you do for North Potomac?"

It is fine to say that public life still exists in old neighborhoods like Gaithersburg. It is another thing to preserve public life and extend it to new development. But land-use planners and a few developers are beginning to heed Jane Jacobs's assertion, "A public life, as far as I can observe, arises out of no mysterious qualities for it in this or that type of population. It arises only when the concrete, tangible facilities it requires are present."

Pioneering architects like Andres Duany began to analyze old neighborhoods to extract the physical principles and dimensions that encourage community structure to emerge from "below the surface" and become public. Joe Alfandre is putting those principles on the ground in the highly experimental development called Kentlands. To their credit, county planners latched onto the Kentlands' "neotraditional" design principles. They tried hard to apply them in the county's part of Gaithersburg, called Shady Grove West. Lack of understanding by politicians and landowners' greed will no doubt prevent them from being fully realized.

But now that we know they exist, they will keep coming up. Schools of planning like that at Catholic University are beginning to teach them. Far from being trivial sentimentality, concerns such as Steve Coll's are leading to a shift in suburban development. PAMELA LINDSTROM Gaithersburg