A subdivision is only a subdivision. But "convention center," "town house complex," "golf course," "arena"--these are words that inspire visions.

I have in mind Patuxent River Farm, a luxurious development proposed for Myrtle Point on the Patuxent River in the town of California, Md. And in invoking visions, I am exaggerating only a little.

For St. Mary's County officials are treating this proposal as something more than a routine request for rezoning.

The plan, named after a real farm that now occupies the 211-acre site, calls for 398 town houses costing $100,000-plus, 98 detached homes at $200,000, a 450-room convention center, a nine-hole golf course, swimming pools, tennis courts and a 400-slip marina.

Such wealth and scale both distress and excite people in this still-essentially rural county. There is concern about possible harm to the Patuxent River, for one thing. But profoundly, the proposed development has reminded the county that it is no longer an unknown corner of the state. People here sense the imminence of change--not of mere addition, but of actual transformation. And they wonder: What form should this new growth take? What do we want the county to look like?

The developers--architect Robert N. Manniello, real estate agent Vincent J. Peritore and developer Cole Hayes--who are from New York, grandly compare Patuxent River Farm to Hilton Head Island, the classy resort off the coast of South Carolina. The developers say the project would result in 350 permanent jobs and 150 part-time and seasonal jobs.

The Department of State Planning, on the other hand, argues the development would require a sewer line that would, in turn, encourage further growth. Along with the run-off such construction always means, pollution of the river would be the final result, the state maintains.

County officials, impressed by the project's quality--as well as by the prospect of $1.2 million in property taxes each year--resent the state's presumptuousness in voicing an opinion, something it rarely does with regard to local projects. Not only does this development respect the environment, say the officials, it will have a lot less impact than if the site were developed in one-acre lots, as current zoning allows.

The irony here is the county traditionally has complained to the state about water pollution resulting from development upstream; now the state sees a problem originating in St. Mary's itself.

Local residents, of course, are divided. Some vehemently oppose the plan. Others are prepared to tolerate it. Still others actively welcome it and accuse the opponents of selfishly wishing to deny outsiders what they themselves--as former outsiders--once coveted. Namely . . . what? The waterfront? The good life? Or, as the Chamber of Commerce slogan would put it, "The Land of Pleasant Living?"

St. Mary's is a peculiar patchwork of a county, where serene farms, ugly commercial strips, waterfront estates, mobile-home parks, bright new subdivisions, ramshackle cabins, mom-and-pop stores and two vast military installations all co-exist. There are suburbs, but no city that spawned them. There are communities (fine, solid ones) and neighbors (loyal, helpful ones) but, it seems, no single larger community to which all, in one way or another, belong.

History has not allowed the county to develop what the psychologists would call a well-integrated personality. After a brief reign as the Mother County of Maryland, St. Mary's lapsed into two centuries of premature senility--or, if you will, recovered innocence.

Then the arrival on the scene of the Patuxent River Naval Air Station suddenly fluffed the county into a confused adolescence, a condition, one might argue, it has not yet outgrown.

People here sense these historical disjunctions and the resulting disharmony, I think. That's why every proposal like Patuxent River Farm seems to have Utopian or apocalyptic overtones. There have been a number of such proposals over the years.

Once there was talk of a "Cousteau Institute," a research outpost run by the famous French oceanographer. Supposedly it was to have been part of a giant waterfront subdivision that never came to pass. Then there was a refinery proposal and later a sludge storage proposal. Both sparked fierce opposition; both died.

More recently, a group of outside developers unveiled plans for Ag Expo, an immense exposition and research center for agribusiness. The proposal made big news for a few weeks, then it faded. Officials are still awaiting details from the developers.

Patuxent River Farm itself recalls another, older scheme involving the Myrtle Point area. The plan was to rezone it for industrial use and develop a deep-water port there. According to informed gossip, Volkswagen was interested in the site. Environmentalists and the Navy resisted. Nothing happened and the VW plant ended up in Pennsylvania.

None of these ideas was insignificant, certainly. But perhaps the sense of urgency they all aroused owed something to a yearning for direction. The county, instinctively aware of its unformed possibilities, wanted a sign, a push toward definition.

Among local officials, the feeling now is that the county has matured. It is ready, consciously, to accept the push, or, better yet, to push itself. The county commissioners seem to entertain every serious development proposal with a certain eagerness.

Like their counterparts throughout the country, the commissioners have embraced the law of the modern civic jungle, that government governs best that shuns fresh tax dollars least, and its corollary: If development doesn't happen here, it will happen somewhere else.

County official Joseph Mitchell put it this way: "To what use are we going to put the county?" Mitchell has just been named head of a new superagency, the Department of Economics and Community Development. The very existence of such a county office--and of such a question--reflects a new sense of expectation. It is as if St. Mary's has reached a certain ripeness.

Brainstorms thrive in this climate. Could St. Mary's City (Maryland's first capital) become a successful theme park? Would a ferry between the county and Crisfield help tourism? Since the dangers of smoking may lead to increased pressure on the tobacco industry, should farmers be encouraged to switch their cash crop to vegetables? Why not grapes?

And what about the continued growth of the high-technology test work being done by the Navy and its contractors at Pax River? Can the county somehow orchestrate for itself that shimmering dream of every hungry municipality in the land, another Silicon Valley?

Other questions ought to follow upon these visions. Will new development benefit current residents? Or will the homes and jobs go to outsiders? What about the poor and unskilled? Does wealth really trickle down? Or do the powerless tend always to lose out?

At stake here, ultimately, is a sense of belonging and a sense of control. Presumably, everyone wants to be included in the future--as a matter of fate, not a victim. History, after all, should be the story of what we ourselves do, not the indifferent story of what happened to befall us.