When President Carter signed the Energy Security Act last week, he called it the "keystone" of his oil strategy. It's been nearly a year since that long, emotional speech in which Mr. Carter proposed to renew the nation's spirit and morale with a forceful energy policy. Since then, the administration, and the country, have made progress toward balancing the energy accounts. But it's useful to keep in mind the nature of that progress and the reasons for it.

In that July speech, Mr. Carter said, absolutely correctly, that the whole energy crisis results from this country's reckless overreliance on foreign oil. He declared that the rapid upward trend in oil imports would be broken. That has, in fact, happened. The record high was 8.6 million barrels a day of imported oil in 1977. Last year's imports were 7.9 million barrels a day, well under Mr. Carter's quota. So far this year imports have been running around 6.6 million barrels a day. That's impressive improvement.

But the reason for it has less to do with American policy than with other countries' prices. What a gallon of crude oil costs 80 cents, as it now does, people use less of it than when it cost 30 cents, as it did 18 months ago. But the side effects of this pressure -- the weakening of the dollar, the deepening of recession -- are not benign.

The United States remains desperately vulnerable to any disruption or decline in the world's oil supply. Further revolution and war in the Persian Gulf region remain the likeliest causes of it. Seven years after the Arab embargo, the United States still has no answer to that one.

Presidents and Congresses seem able to make provisions only for the distant future -- and it was toward the distant future that Mr. Carter's July program was directed. It required four pieces of legislation. The windfall oil tax is now in place, and it is a stronger and better tax than the administration's original proposal. The Energy Security Act will provide broad loan and price guarantees to accelerate the production of synthetic fuels. It also establishes additional subsidies for conservation and for the development of solar energy. That's the more urgent legislation.

There's also a bill to force utilities to switch oil-fired boilers to coal, but it's coming along slowly. There is the bill to assemble the patented dandy corner-cutter, the Energy Mobilization Board. It's been derailed in the House, possibly permanently. Wrong in principle, its absence will do no harm. Altogether, Congress has improved an enacted the best of Mr. Carter's program and balked at the worst. That's not a bad showing.

But Mr. Carter's great contribution, and a crucial one, has been not the legislation. It is his dogged insistence that the oil shortage is real, serious and continuing. In contrast with his two predecessors, Mr. Nixon and Mr. Ford, he has continued to press this unwelcome truth with stamina and determination. The real change in the past year has been a matter of attitudes -- a widening acknowledgment that Americans have to do more with less oil. The gasoline lines have vanished only because Americans are now using much less gasoline than they did a year ago, at the height of the shortage.

Last July's speech, contained the remarkable sentence, "Energy will be the immediate test of our ability to unite this nation and it can also be the standard around which we rally." By that standard, the past year must have been a profound disappointment to him. The old quarrels and divisions continue. But, divided as ever, the country is gradually adjusting to less oil. The question now, as a year ago, is whether there's enough time for an adjustment that is only very gradual.