With some justification, political observers are agreeing that last week's summit was merely a public relations spectacle put on by President Reagan and General Secretary Mikhail Gorbachev. Indeed, no progress was made in arms control or on regional issues such as Afghanistan and Angola.

Skeptics argue that the summit was designed to strengthen Gorbachev's hand for the upcoming Communist Party conference. This meeting is crucial for the Soviet leader, who will seek approval of measures to loosen Moscow's grip on industry and daily life, to democratize the Communist Party, and to strengthen freedoms of speech, conscience, and assembly.

Likewise, these nay-sayers claim the summit merely served as an opportunity for Reagan to guarantee his place in history and shore up support for his last months in office.

BUT by underscoring a new era of detente, the summit's impact was enormous--at least on the issues of arms control and superpower relations. In the last few years, Reagan has changed his tone, from bellicose hostility to pragmatic moderation. The mutual suspicion and lack of dialogue that characterized U.S.-Soviet relations during the early years of this administration have been replaced by a sober, though still wary, relationship.

The dominant rhetoric of Reagan's early years in office--grim warnings about the communist menace, invocations against the "evil empire" and denunciations of America's supposed "cave-in" to the Soviets during detente--has suddenly become passe.

The President has repeatedly expressed his admiration for Gorbachev's efforts at glasnost and perestroika. He has met with the Soviet premier four times in the last two years and hammered out a verifiable arms control accord which sailed through the Senate with relative ease. The once-fervent anti-communist even scolded hawks and former bedfellows like Sen. Jesse Helms (R-N.C.) for their stubborn resistance to any semblance of an arms control treaty. This shows just how far Reagan has come from his we-can't-negotiate-with-communists crusades of a few years ago.

THIS new era of detente will not produce a democratic Soviet Union, but it will advance arms control and produce a healthy era of coexistence unlike anything we have seen in recent years.

Of course, this turnaround is ominous to conservatives, who fear that Reagan has become senile in his old age and is no match for the skillful Gorbachev. The new reforms, they argue, mask Gorbachev's plan to revive the stagnant Soviet economy and rival our technological capability. What they fail to realize is that a paranoid Soviet Union presents a greater threat to world peace than one that openly recognizes its past atrocities and encourages the expression of different views. An economically weak military superpower would be more likely to play off its area of strength; so America should welcome relations on an economic level, not in a war zone.

No one should swoon over Gorbachev and confuse him for a liberal reformer intent on bringing political freedom to the oppressed peoples of the communist bloc. Nor should one forget that a bloated bureaucracy and an entrenched party still present formidable obstacles to Gorbachev's reforms.

ONE should be skeptical of Gorbachev's claims that the horrors of the Stalin regime were an aberration from Soviet socialism. After all, Gorbachev and his colleagues still glorify Lenin, who effected one-party dictatorship, the subordination of justice to expediency, and the use of terror as an instrument of control.

Yet even the most hard-line conservatives should be willing to admit that the Soviet Union's current changes represent progress. To argue that a virulent anti-communist like Reagan has suddenly turned naive is ludicrous. Such assertions carry about as much weight as the Kremlin's denunciations of human rights abuses in non-socialist countries.

Nor should liberals hesitate to credit the Reagan Administration for taking part in and encouraging this watershed period in superpower relations. Remember those early associations of a trigger happy Reagan with the spectacle of nuclear war?

What we've seen during the last week is the final step in a remarkable evolution, both within the Soviet Union and within the Reagan Administration. Though the summit brought no immediate, tangible results (very rarely do summits anyway), it did reveal how far the superpower relationship has come during the last four years.