Soviet President Leonid Brezhnev let Western Europe understand last week that he would take the diplomatic high road for now in responding to President Reagan's readiness to use military strength abroad, an apparent initial reversal of the Soviet strategy of using raw power to confront the Carter administration's diplomatic and political initiatives.

Brezhnev did this by hauling the idea of a superpower summit conference out of the diplomatic deep freeze, where it has languished in the 14 months since the Soviet invasion of Afghanistan shocked Western public opinion and brought an end to the most optimistic hopes for detente. Bonn, Paris and London were probaby the targets of the Soviet leader's suggestion as much as Washington was.

Whether by coincidence or otherwise, the unlikely idea that high-level summitry could restore life to detente now also had been advanced a few days before Brezhnev's speech by an informal suggestion in this newspaper from the Western leader who knows Brezhnev best, French President Valery Giscard d'Estaing.

Giscard is turning over in his mind the prospects for an East-West summit late this year that would apparently resemble the kind of four-power conclaves held in Geneva in 1954 and 1955 that were brought to an end by the ill-fated Paris conference of 1960, which was aborted by the U2 incident.

This stress on East-West summitry now is paradoxical not only because of the Reagan administration's clear disinterest in rushing to talk with a Soviet leadership that it has just branded as treacherous and evil, but also because of the emerging signs that Western leaders are cooling significantly to the kind of seven-power summit among themselves that took on such importance during the Carter administration.

Reagan does not yet seem to demonstrate the kind of confidence that Carter evidenced in the notion that personal contact and persuasion among peers could resolve almost any problem. Moreover, Giscard, who originated the industrial democracies' summit by hosting the first one in Rambouillet, France, in 1975, now feels the gathering has lost much of its usefulness because its size and scope have been expanded.

Expectations built up by media attention now exceed the ability of the leaders to deliver, Giscard believes. France also doubts that meetings attended by countries seen in Paris as marginal to the world power game -- such as Japan, Italy and Canada -- can produce the kind of decisions that have to be made now by the United States, Britain, West Germany and France.

Behind Giscard's willingness to advance the idea that renewed Soviet-American dialogue at the summit is the highest possible priority item of business lies as assessment of Brezhnev and his goals that is in sharp contrast not only to the sentiments voiced by those now in power in Washington but also to the view of Soviet intetions held by many high-ranking members of Giscard's administration.

The French leader appears to feel that Brezhnev can be reasoned with on a personal level and can be persuaded to intervene, when he is in good health, against any reckless and malign elements with the Soviet leadership. Giscard does not believe that the Soviets are behind a campaign of international terrorism or expansionism, as the Reagan administration feels.

The Soviets, in Giscard's view, have been rushing into vacuums left by the Carter administration during the last four years while it pursued friendship with Third World nations and sought to avoid military involvements. The Kremlin countered by projecting military power abroad, not only in Afghanistan but also in the Horn of Africa.

If that view has validity, Brezhnev can be expected to react differently to the assertive approach coming from Washington now. He is not likely to let Reagan choose the ground for the first phase of the competition, and seems to be consciously switching to something approaching a peace offensive that would let his propaganda officers in the Third World and Europe draw a contrast between his words and those of Reagan and Secretary of State Alexander Haig.