LONDON — London. - The mercurial philosopher I live with complains of what she describes as ''the conspicuous consumption of ideas'' she discerns here. ''How far do you have to travel to find a new perspective?'' she asks.
There appear to be only a certain number of correct issues at any given time that the media find savory enough to chew over and thus encourage their consumers to do the same. In London, the current talking points (I had better get these down before they change) are abused spouses of both sexes, rain forests, the disadvantaged children of single parents and the movie ''Thelma and Louise,'' or the phenomenon of ''femachismo.''
Some of these issues were on the agenda in the United States hardly a season ago, though probably they have gone off, like cantaloupes left too long in the refrigerator.
These are all important concerns, of course. People should talk about them, and their implications for the way we live. But the discussion, as it is carried out here, seems to have the unserious fragrance of fashion about it.
But, then, London, with all great cities, is both a slave to, and incubator of, fashion -- not only as it relates to dress, but to ideas, serious and frivolous, and the adherence by large groups of people to a single trend of thought.
Trends are defined by their transience, and I think ''Thelma and Louise'' might be about ready to drop off the chart.
At the moment, in addition to the list above, there is another trend evident among some Londoners: the impulse to denigrate this sparkling city.
The tendency seems especially strong among those who might other-wise be regarded as the heirs to Boswell, those who would normally celebrate life here. Among them are Clive James, a kind of media gadabout, and Paul Barker, a journalist.
Mr. James went on the BBC recently for about an hour during which time he interviewed several of his friends of 30 years -- thick and prosperous every one of them-- at interesting venues around town (such as an abandoned newspaper plant on Fleet Street whose reporters were remembered for turning in stories ''even more improbable than their expense accounts'') and all concluded that London is just not the place it used to be-- when they were young and hungry.
The spark that warmed their memories had been snuffed. There were too many people hanging around in the parks and squares. Mr. James couldn't understand why so many foreigners made their way here. Or why the underground trains didn't run on time. Why Oxford Street was still so crowded with tourists. Or why a pigeon would spot his suit in Trafalgar Square.
Mr. Barker did his work in an article in the Evening Standard Magazine. It asked, ''Is London Dying?'' His every sentence suggested that, yes, it is: ''Its shops and offices lie empty, its streets are filthy, clogged and dangerous and its people increasingly homeless, unemployed and desperate . . . ''
People like Mr. Barker take New York (and by extention, other American cities) as their model of utter degeneration. That's the way we're headed, is the line. Don't the potholes prove it?
Well, having recently made my way from one of those niches in hell, I'm prepared to argue that things are not so bad here as Mr. Barker and Mr. James say it is.
London has reached nowhere near the level of urban decay as New York, nor even of Calcutta or Lagos. People are very civil, even polite. You don't have to suspect the intentions of people who just sit in the parks. Most of the citizens go about unarmed.
There are a lot of foreigners here, from the Middle East, India, Pakistan, the Caribbean, the United States. They are the children of the defunct empire come to feed off the mother country, possibly to make it live again by having British-born children so they can grow old assured of someone's care, and sit in the parks themselves and feed the increasingly aggressive pigeons.
(Incidently, one of the suggestions for improving life in London, offered by disco owner Peter Stringfellow, was, ''Kill all dirty and diseased pigeons.'')
About the only thing worth saying about the observation that there are too many foreigners here is that they have improved the food.
London is a big city and, as such, an arena for both fulfillment and disillusion. Among the disappointments it offers is the sight of so many young people determined to defeat their own natural beauty. This they do by tattooing themselves up and down, pushing rings through their nostrils and shaving the hair on their heads into weird patterns, then dyeing it even weirder colors.
When the young women do it, the effect is truly unfortunate. But when the young men do it, now and then they achieve degrees of hideousness that are strong enough to kill grass.
After a while you find yourself trying to predict what people will be talking about next. It's like a game. One subject that seems to be inching over the horizon is the dolphin.
(Not too long ago, the elephant was the animal most dear to Londoners. But last week the Saturday Review magazine in The Times came out with a cover story that asked, ''Are We Being Too Sentimental About Elephants?'' Sic transit . . .
A group of actors and other celebrities announced they are banding together on behalf of the dolphins. A few weeks ago, celebrities banded together on behalf of the homeless and slept a night out in London in cardboard boxes. They all got their pictures in the papers.
So far the dolphin celebrities have not declared their plans, but the media remain poised.
Another widespread anticipation was for the start of the grouse season, today. Now it is permitted to shoot them. Everyone was looking forward to it. But not the grouse.