Triple witness is borne in the bizarre remarks volunteered the other day by President Carter regarding countries where he intends to contest Russia for influence.

The statement demonstrates, first, that Carter continues to think - and, worse, say - dumb things about foreign policy. It suggests that he takes little or no counsel from experience or advisers. Finally, the episode shows how overindulgent and uncritical most of us in the press and television have been in dealing with the no longer very new President.

Carter made the remarks I have in mind in an interview with members of the Magazine Publishers Association last Friday at the White House. In his opening remarks, the President said:

"My own inclination . . . is to aggressively challenge, in a peaceful way, of course, the Soviet Union and others for influence in areas of the world that we feel are crucial to us now or potentially crucial in 15 or 20 years from now. That includes places like Vietnam, and places like Iraq, and Somalia and Algeria and places like the People-s Republic of China and even Cuba."

Though Carter is rarely dense in his articulation, those remarks are not altogether easy to follow. But I find it impossible to resist the conclusion that he intends to compete against Russia for influence in the list of states that he deems "crucial to us now or potentially."

In fact, the list makes almost no sense at all. The great lesson of the Vietnam war and its outcome was that Vietnam is not, and never will be, crucial to American interests. Neither are Iraq, Somalia or Algeria. Indeed, they are so far from being of vital interest to the United States that it is hard to understand how they made their way onto the list at all.

Then there is the very strange inclusion of COmmunist China. Is Carter under the illusion that the Peking regime is somehow composed of Russian stooges? If so, that will be big and welcome news in Moscow.

No doubt Cuba is a place where the United States has an interest that would be well served by curbing Soviet influence. But even that purpose is not advanced by trumpeting the intention. On the contrary, by saying out loud what might be thought with some discretion, Carter only plays into the hands of the suspicious Cuba hard-liners who want to resist closer ties with Washington.

Finally, of course, there is the impact on the Soviet Union. Once more Carter lays down the gauntlet to the Kremlin. Once more, for the sake of verbal fireworks, he poisons a relationship that - except for his various blunders and bloopers - could be relatively smooth and extremely useful.

But where does the President get these outlandish ideas? Certainly not from the cauldron of experience. The harsh rejection by Moscow of the two arms-control proposals advanced by the administration in March teaches what was supposed to have been a dramatic lesson in the high price paid for aimless popping off.

Secretary of State Cyrus Vance obviously knows much better. So does Zbigniew Brzezinski, the President's national security adviser. So it's something of a mystery why they are not pounding the table insisting that sensible policies not be compromised by the rhetorical instincts of the President and his ambassador to the United Nations, Andrew Young.

But Carter's advisers are not alone in playing mute, inglorious Miltons to his fatuous comments. None of the magazine publishers present when he made the original remark asked him about it. One tender question was posed at his news conference Monday, which Carter answered by repeating his original remarks and adding Ethiopia to the list of "crucial" countries. That's not exactly rough treatment. So it's not entirely surprising that in the field of foreign affairs Carter keeps preaching his own original, untutored gospel.