London — One of the most familiar, accepted, and yet elusive themes of Western society has been surfacing here again. Some blame it for all Britain's ills. Others claim that it has ceased to exist.
But everyone knows about it, and everyone, it seems, has an opinion.
The theme is class or, more accurately, class distinction. It is a favorite topic at Labour Party annual conferences, both in the usual sense, and the Marxist one. It runs throughout the current debate on Britain's role in the world.
Is class still strong in British society? Or does it count for less these days? Does it help the country, or retard it in a contemporary world?
''Of course there is class,'' said a delegate to the recent Conservative Party conference in Brighton. ''It's the way you are educated, who your parents are, your taste and style. It can be your money, but not necessarily so.''
''Class,'' says a British trade unionist, ''is what keeps the bosses on top and us workers down.''
But a Lancashire bank official at lunch the other day disagreed. ''Class is just differences between people,'' he said. ''You find it in every country. 'Class' is a slogan people use when they want to blame Britain's troubles on something.''
One scholarly view, argued by Prof. John Westergaard and sociologist Henrietta Resler in their recently reprinted 1975 book ''Class in a Capitalist Society,'' is that class is indeed still alive and well in Britain.
The book defines class not as a mere preoccupation with social ranking but basically as ''the cleavages of economic position, power, and associated chances in life.'' Private property, profit, and market, it believes, still dominate social position.
The increase in state activity, labor's counterpressure against management, and more opportunity and education for more people have not really lessened social inequality, the argument goes, but have continued them.
To a newcomer to Britain such as myself, old definitions of class are changing. But social divisions are still strong.
Class used to revolve much more than today around royalty and nobility. Aristocratic birth brought property and privilege. Money generated by ''trade'' might buy comfort but never true class.
Today, a thin layer of aristocracy still hunts foxes and goes to glittering balls. But money now counts for more. Achievement, not just birth, earns privilege. Life peerages go to trade union leaders, such as the miners' Joe Gormley. The idea that social class precludes the need or the wish to make money as an entrepreneur has lost much of its force.
In the more egalitarian United States, money is often synonymous with class. Sociologists Richard F. Coleman and Lee Rainwater compared Boston and Kansas City in the 1970s and detected seven layers of class, American-style: old family rich, new rich, college-educated professionals and managers, comfortably-off middle America, less-well-off middle America, the working poor, and the welfare class.
Here in Britain, some of the same trends have begun.
Because more people have more money than ever before, they don't have to be a lord to own a Rolls-Royce or a spacious home, or a Savile Row suit. The man who delivers milk bottles to my door every morning has just returned from a vacation on a Greek isle.
Other symbols change. You can still tell people by their accent, but regional accents are far more accepted today. The BBC and commercial television and radio no longer concentrate on the familiar rounded tones of the Oxbridge graduate but use a variety of accents instead.
A major shift is in education. It has long reinforced class differences, but now it does so differently. Britain is more of a meritocracy than an aristocracy than ever before. It remains true that only a small number of British 18 -year-olds ever go to university at all - 7.5 percent in 1981, according to figures just released by the Education Ministry. The percentage is far lower than in the US, France, or West Germany. Even when the educational elite is widened to include all forms of higher education, it rises to only 12.3 percent.
Yet the path to Oxford and Cambridge lies mainly through academic prowess today, rather than family connections. ''And the academic level required keeps rising in standard as the competition increases,'' says the headmaster of one elite school. There are also fewer places, as the government reduces its block grants to universities as part of its overall economy drive.
Teachers report that the dream of many a middle- and lower-class family is still a scholarship to Oxford, Cambridge, or another ''good'' university. Class has something to do with it, but so does success, and the ability to find prestige jobs that pay well.
Judging the extent of change is difficult. The issue of class is often disguised by historical cliche. Also, the political left wing, whose rhetoric sets the framework for a surprisingly large amount of public debate here, tends to exaggerate its importance by constantly criticizing it.
Large social gaps still exist between lords and laundresses, but Britain seems to be growing more middle class in its social structure, and certainly in its ideals. Even in the poorer north, unemployment and recession merely emphasize the rising middle-class standards of most people, from private home to central heating to a holiday abroad.
At the same time a new industrial elite constitutes a fresh layer of class. Across the dinner table the other night sat a hard-driving, energetic example. Tall, in his 40s, he develops markets for his company's products all over Europe. He works 18 hours a day, earns large commissions on top of a generous salary, lives in a fashionable house, and has a country cottage in Cornwall. He considers himself no one's class inferior despite his lack of ''noble'' birth.
In class, as in other things, Britain changes slowly. A British container ship taking me from Helsinki to London had three separate dining tables (for captain, chief engineer, and junior officers), whereas the Finnish sister ship had only one.
A truck driver complained to me that he never saw the big bosses down on the shop floor, only foremen. He has no wish to be upper-class, however. He already has his own home, two cars, a motor boat, and a steady sense of self-worth.
Change may be slow, and change may be disguised, but change is taking place. Britain's class differences are not fading away but they are taking different form.