Buildings, after they are built, possess a seeming inevitability. This is almost as true of bad buildings as of good ones. Nonetheless, buildings are ideas before they become buildings, and people who design them are faced initially with a blank sheet of paper and thousands of choices to make.

This is the entry point for "Ideas, Ideal, Deal, Real," an exhibition at the School of Architecture Gallery at the University of Maryland. The show consists of drawings, photographs and models of six buildings recently designed by six nationally known, non-Washington architects: Gunnar Birkerts, Alan Chimacoff, Cesar Pelli, Robert A. M. Stern, Stanley Tigerman and William Turnbull. Because each project is presented from inception to near completion with steps in between, the exhibit offers a rare opportunity to observe sophisticated architectural minds at work.

The exhibition was not organized with the layman in mind -- anyone not at ease reading floor plans and elevations would find it near impenetrable -- nor does it always provide the kinds of information concerning costs, client, climate, site, architectural context and legal constraints that many of us would find handy in evaluating the projects. Even so, it is a worthwhile effort that professionals and architectural amateurs of all ages will find especially attractive.

With these six examples the exhibit demonstrates that diversity -- of intention, process and style -- is the outstanding characteristic of American architecture at this late point in the 20th century. This is an exceedingly healthy condition, not simply because reasoned argument is good for the soul in general, but because when conducted by skilled, responsive architects, it augurs well for our cities, suburbs and small towns.

"There are as many ways to comprehend [the] present as there are minds to comprehend it," writes Gavin Macrae-Gibson, an architect, in Perspectiva 21, the current issue of the Yale Architectural Journal. "There can no longer be one sensibility that reveals the truth of the age. Instead, many sensibilities compete to express our industrial culture with validity."

Amen. Downtown Washington west of 15th Street, Rosslyn and Crystal City are by no means isolated examples of the harm done to our environment, our patterns of living and our collective sense of self-worth when the esthetic orthodoxy of modern architecture, the parallel orthodoxy of modern urban planning and speculative economics are insensitively combined and applied.

"Post-modern" is what the new architectural sensibility most commonly is called, although that may be too prideful a term and too closely associated with the allusive styles of a few architects (Stern, Michael Graves and several others). But the architectural attitudes we see all around are welcome by whatever name. These include a new openness and freedom, an increased responsiveness to the environmental implications of building, a renewed respect for the lessons of history and an enhanced appreciation of the complexity and delicacy of the connections between new construction and existing streets and buildings.

Each of the buildings in the Maryland exhibit illustrates certain aspects of this new sensibility, which is not a question of style. Four building types are represented: suburban speculative office buildings (designed by Chimacoff and Stern), university classroom buildings (Birkerts and Pelli), a downtown showroom and office complex (Tigerman), and a social club (Turnbull).

Speculative office buildings, particularly in suburbs where there is not much architecture from which to take stylistic cues, are special challenges because they always begins as neutral boxes. Thus the contrast between Stern's design and Chimacoff's is especially interesting, even though the conditions were quite different.

Stern's commission was for a spec building par excellence, located hard by the Massachusetts Turnpike, while Chimacoff's, though subject to similar economic exigencies, was part of a university-inspired experiment in solar energy design.

Stern clearly started, and ended, with the idea of creating a building with a galvanic "old-new" image, running the box through a variety of stylistic changes (from Egyptian to Greek to Italian Renaissance to 19th century Italianate). Chimacoff just as obviously wanted to give his building what he thought was a more appropriate, contemporary, rectilinear skin. The result is that Stern's building will stand out almost like a sign saying "Past and Present," while Chimacoff's will take its place more matter-of-factly. But each architect spent much of his creative energy where it would count most: on parking (lots with lots of trees), on placement within the site (each created axial entranceways) and on lobbies (Stern even taking the opportunity to design a tour-de-force stairwell).

The university buildings contrast more strongly in approach and result. Birkerts, in his design for the college law building as a cap for a prominent hill on the campus of the University of Iowa, seemed to start with a form in mind -- a circle, which he saw as a "fitting symbol for the profession of law" -- and then to squeeze in the necessary functions while whittling away at the cylindrical structure. When finished the building may be broodingly beautiful (and maybe not), but it likely will seem even more arbitrary (and less free-spirited) than Stern's office building as Doric temple.

Pelli's building for Rice University, containing classrooms, faculty offices, a library and a lecture hall, is something else again. In this sequence of drawings -- site plans, floor plans, elevations, materials studies -- and photographs of models, we see an impressively subtle development that takes advantage of the Beaux Arts campus plan (laid out by Ralph Adams Cram early in this century), the strong architectural context (Cram's original Mediterranean style buldings) and the separate but related functions. The result is an extremely beautiful building that manages to unite old and new with seeming effortlessness. Its environment, we might say, fits it like a glove.

Tigerman was commissioned to design a one-story showroom for the design-hip Knoll company in downtown Houston, and this he did with a certain understated resolve, taking pains to create a semi-ceremonial space inside and to give the shed a crisp, colorful, gridded skin with a sign-like pediment at the main entrance. The more interesting aspect of his effort, however, is its emphasis on urban design. Whether he was asked to or not I can't say, but what he did was to design the entire block as a consistent, interconnected whole, complete with parking lot and flanking office towers. It makes a spiffily intelligent ensemble that someone ought to build.

The remaining piece was an architect's dream come true: Turnbull's commission for the American Club in Hong Kong, situated high on a spectacular cliff overlooking Tai Tam Bay. He performed brilliantly, too, playing around with the grade changes on the site and the many functional needs (parking, tennis courts, a bowling alley, restaurants and so on) until they fit together like a perfect puzzle. In the site plans and model photographs this concrete building, with arcades and turrets in just the right places, complements its beautiful hill, which, as any honest architect will tell you, is much easier to say than do.

This refreshing show, organized by Roger K. Lewis of the Maryland architecture faculty, is open from 1 to 4:30 p.m. on Tuesday, Wednesday and Friday, and on Sunday from 1 to 5 p.m. in the Architecture School Gallery on the College Park campus. If directions are needed, phone 454-3427.