Back in the first century A.D., it was the wisdom of the Roman philosopher, Seneca, that, "Joy is a very serious matter." Precisely, and let it be noted here that there has been no trivializing in the mood created by the Redskins and the final whistle in San Diego. No compromises. The Redskins are the greatest. Redskins fans are the greatest. Washington is the greatest. Love that Doug Williams. Love Timmy Smith. Love thy neighbor, if he loved the Redskins. If he doesn't, drop him. Like a leper.

Where has there been any city anywhere, so joyed, so pumped-up, so joyful in its embrace of its football heroes? When on Sunday at San Diego Jack Murphy Stadium, the closing number was 42-10, Redskins, it was everybody winning the lottery, everybody getting a Super Bowl ring. For the last three quarters, every television set had been a place to worship. Later it could be enshrined.

Was Washington ever so gripped by any other happy event in its history? Oh, they'll mention Oct. 10, 1924, when Walter Johnson came off the bench in the ninth to pitch those four wonderful scoreless innings that clinched the World Series against the New York Giants. And old folks will also remember the parade up Pennsylvania Avenue that was so big and exciting, and there is a memory, too, of the exultant crew riding the Cherrydale, Va., Hook and Ladder Co. float and flaunting the banner: "Let Cherrydale Burn!"

But Washington was then a small town, 400,000 souls and not many in the suburbs. In 1924, it was a celebration. In 1988, it was an explosion, in a community of 3 1/2 million, fed for weeks by a television and newspaper blitz whetting the populace's expectancy of the Super Bowl. It was saturation-penetration, effecting a mass high, and slyly holding out the gorgeous possibility that the underdog Redskins could win this one. Win the Super Bowl. Bring on the opening kickoff. Hail everybody.

Denver played into the hands of Washington's millions by creating the classic suspense factor, a touchdown pass on its opening play that only made the Redskins' final victory sweeter, the TV viewing more jubilant. In the last 58 minutes, against those adjusted Redskins defenses, John (No-Way) Elway would never throw another touchdown pass.

O. Henry could not have scripted a more improbable turnabout than Williams'. In the first quarter, he couldn't move the Redskins out of their own territory and they were a mess. He also went down, hurt, on one of his drop-backs, his left knee twisted beneath. A protruding leg was there for all to see, and so was the agony written on Williams' face. Hideous memories of Joe Theismann. Was this another quarterback's career ended in public view?

Would Williams ever return to the game? Yes, quickly, and before long there was that 80-yard touchdown pass to Ricky Sanders. And before the second quarter was over, there were 35 Redskins points on the board. Four of those five touchdowns came out of Williams' pitching hand. And if Smith had not insisted on taking a simple handoff and going 58 yards into the end zone, Williams might have had all five.

For weeks, out of Denver had come the ominous reports of the Broncos' Three Amigos, their wide receivers who would grab off Elway's passes no matter what the defenses, and be touchdown-bent. Amigos-shamigos. It is not civil to gloat, so we compliment them on the six passes they caught, collectively, which are exactly two-thirds as many as Williams' nine completions to Sanders alone.

In the record-setting parade on Wednesday, Washington properly lionized all its heroes, Williams, Sanders, Smith, Dave Butz, Dexter Manley, Gary Clark, Barry Wilburn and all the others. They were filling a need for a significant Redskins victory in the Super Bowl after that degrading 38-9 rout by the Raiders in Super Bowl XVIII.

Last Sunday they were in need of a transcendent hero to remove the stigma of that Super Bowl humiliation, and they found him, and his name was Doug Williams, and he also dispatched all that stupid calumny about black quarterbacks. Doug Williams. The Great Emancipator.