A congressman friend of mine likes to indulge in imaginary letters to his constituents. This, in response to a flood of anti-tax mail generated by Proposition 13, is his latest effort :

Dear Constituent:

Thank you for the "message." You say you are "fed up with big government, big spending, big taxes." I don't blame you. But before I rush into action, I need a little guidance on your priorities. Am I, for example, to consider you latest communication as canceling previous messages you have sent me in behalf of bigger and better federal services?

I will certainly do everything I can to get you, simultaneously, both reduced taxes and increased services, but in case this is not feasible, I would appreciate some clarification on just what services you want eliminated in order to carry out you tax-cut instructions.

The Pentagon budget, of course, offers the single biggest opportunity for savings, but I know you don't want to trifle with the security of the United States. I remember how upset you were when I tried to save some billions by opposing the B1 bomnber, additional nuclear carriers and ever larger Trident submarines. I've learned my lesson, so don't worry, I am not going to offend you and other patriotic constituents by trimming the defense budget, which this year will climb to $126 billion and surpass $150 billion by 1980 or so. Nevertheless, as you wired me, we've got to stand up to Russians.

You don't need to be concerned, either, over my trying to trim Social Security benefits. I agree with you in the past they have been much too meager, and I am glad that you approved of my efforts to put the Social Security system on a sounder basis. This, of course, is going to cost about $200 billion extra over the next few years, but, as you say, the American people are entitled to protection in their old age.

Some of my constituents think it's time to abolish our expensive unemploment-compensation system, which has been costing around $20 billion a year, but I remember a touching letter from you saying how this system had saved the family of your brother-in-law when he was laid off, so I guess we better keep that going, huh?

I've been getting mail from city dwellers who think we ought to crack down on agriculture supports, but apparently they don't realize that America has the most efficient and cheapest farm and food system in the world. If the government let our agriculture collapse, the cost would be astronomical in both money and misery.

Our interstate highway system, admittedly the finest in the world, is immensely costly, but every time we in Congress try to cut it back we get a flood of protests from the taxpayers. It's the same with environmental protection, industrial safety and public health. A glance around the world shows you can't reduce public health standards without reducing life expectancy.

Like you, I am a war veteran, so I share your view that veterans benefits, large as they are, should be still larger. You are on target when you say the GI bill of rights, which put millions of veterans through college, has been a splendid national investment.

Over the years, I find that many of my constituents believe their taxes could be cut if we "cleaned up" the welfare rolls and got rid of the "bums." Actually, around 90 percent of the welfare dollar goes to children and the mothers who must look after them. Even if federal aid was abolished altogether, it would produce only a minor tax cut.

A lot of people, especially the middle classes, seem to think that high taxes are depriving them of the pleasantries of life. Only today, however, I received a report showing that Americans spent $160 billion last year for "leisure and recreation," and this huge figure is expected to exceed $300 billion a year by 1985.

Yet President Carter and the Congress are now shying away from a national health program on the ground of cost. Is it possible that the richest country on earth cannot afford the kind of health care that nearly all the other advanced nations adopted long ago?

I have two other clippings in front of me. One reports the closing of summer schools because of the "tax revolt"; the other reports the opening of more big gambling casinos, where the public is throwing away millions of dollars each day.

Congress will soon cut the income tax by at least $15 billion. This is on top of tax cuts of $20.4 billion in 1977, $27.6 billion in 1976, $28.6 billion in 1975, and $11.4 billion in 1971. If the rates of 15 years ago were still in effect, U.S. taxpayers would be in a state of shock.

Few seem to realize that Americans already enjoy, with minor exceptions, the lowest taxes in the developed world. The latest data show that the total tax bill for U.S. citizens is merely equal to 29.6 percent of the national output. In West German it is 36 percent, in Britain 37.4 percent, in France 39.1 percent, raning upward to 50.9 percent in Sweden. The only major country with a rate lower than the United States is Japan.

In closing, I would like to thank you for calling my attention to the new Kemp-Roth bill to cut income taxes by one-third. The sponsors claim it would stimulate the economy and generate enough new federal revenue to make up for the cut. Why not, then, cut taxes by two-thirds or abolish them altogether? It can be done. The Hottentots have done it.

Justice Oliver Wendell Holmes, who preferred our society to the Hottentos, once said that he was glad to pay taxes. They were, he said, his "investment in civilization." To tell the truth, Dear Constituent, that's the way your congressman feels, too.