The acrid aroma hanging over the Communist Party congress was the old incense of the communist church: burnt reputation. Gorbachev trashed the reputation of Brezhnev, as Brezhnev had done to Khrushchev, who did unto Stalin . . . world without end, amen.

In the aftermath of the dreary congress, the trajectory of Gorbachev's reputation in the world will be compressed. The steepness of its decline will mirror its sharp but short rise during his first year. Now the United States must design a policy for the opportunities and dangers to be posed by the accelerating decline of the Soviet Union in the Gorbachev era.

Gorbachev's historic role will be to kill the illusion that makes him seem, temporarily, more interesting than he is. The illusion is that the Soviet system is plastic to the will of the leader, and that leaders come with diverse wills. Actually, the leader is, inevitably, an expression of the system that molded him as he rose through it. Problems blamed on the physiognomies of decrepit leaders are now going to be seen as deriving from the unchanging ideology that rationalizes and makes primitive the self-replicating ruling class.

Gorbachev has turned a scowling face toward the party -- the only instrument for controlling the state -- and said simply: Control better. Indeed, at the conclusion of his five- hour speech to the congress he praised "heightening the vanguard role" of the party.

Gorbachev wants to achieve economic rationality without an economic market, and with a command economy. That is impossible. He denounced industries that manufactured goods "for warehouses," meaning without regard for consumer demand. But consumer demand is irrelevant in a state run by a party with the "vanguard role" of pulling the benighted people to their "real" interest, which is the convenience of the state. Admit the principle of consumer sovereignty and the seamless web of Soviet tyranny would unravel.

Here, then, is the paralyzing paradox of Soviet society. It is supposed to be a collectivist society ruled by "science" rather than individualist interests. Yet the interests of the individuals in the ruling class require the pretense of a "science" of progress that is the basis of that class's claim to privileges.

It has been said that the problems confronting the industrialized democracies are solvable by policy changes, whereas Soviet problems require systemic changes. Nothing announced or even foreshadowed at the congress suggests such change. So the Soviet crisis of congealment will continue, and the Soviet Union will become decreasingly suited to the modern world.

Pat Moynihan says the delicate U.S. task is "managing the decline" of the Soviet Union. "For as they come to sense they are doomed, they must become ever more dangerous." Henry Rowan of the Hoover Institution, writing about "living with a sick bear," says the interest of the West is in "letting the Soviet system decay."

One reason Moynihan stresses Soviet decline is to correct conservatives "whose disposition is to angst: the decline of the West, the rise of the SS-18." Rowan, a conservative, stresses Soviet decline to counter the liberal agenda. He argues that Soviet "economic sickness, as opposed to negotiations on arms, is a much more promising path to achieving an improvement in our security."

The Soviet Union has passed the apogee of its doomed attempt to keep pace with the West. As the world becomes more complicated and rapidly evolving, it requires of societies fluidity, adaptability and other prodigies of freedom. The Soviet Union will see the gap between it and the democracies widen -- if the democracies keep their nerve and keep the pressure on.

One Soviet strategy will be the combination of parasitism and cynicism known as d,etente: more subsidized trade with the West, more purchases of technology, more espionage, more anesthetizing of Western publics. The West may think, yet again, that d,etente, which the Soviet regime desires as an alternative to systemic change, will stimulate such change. Or, the West may offer d,etente to assuage Soviet desperation that could result in a lunge for supremacy through aggression.

The sensible way to respond to Soviet decline is by hastening it. Policy should be: no d,etente, and more of the Reagan Doctrine of increasing the cost of the Soviet empire by supporting insurrections at the margins of the empire (Afghanistan, Nicaragua, Angola).

The Soviet Union is no longer (in Churchill's words) a riddle wrapped in a mystery inside an enigma. It is conspicuously an invalid trapped in a bureaucracy drunk on a 19th-century fallacy, Marxism. It is a system being driven toward suffocation and anemia, its deserved destinations.