Some time-tested sports lessons are relearned in unpredictable Philadelphia-Boston playoff series

There were lessons about sports, character, human nature, and just about anything else you wanted to learn in this year's showdown between the Philadelphia 76ers and Boston Celtics for the National Basketball Association's Eastern Conference championship. Indeed, one might describe the dramatic, seven-game struggle in which Philadelphia finally emerged victorious as the definitive textbook on such matters.

The first lesson was one that all coaches and players learned a long time ago , but that few writers or fans ever seem able to grasp no matter how many times the evidence is hammered home to them. In baseball it is embodied in the time-honored axiom that ''the game isn't over until the last man is out.'' And although other sports may not have slogans to match, the message about the unpredictability of athletic contests is the same in all of them.

There have certainly been plenty of examples through the years -- including last spring's version of this very same series. The Celtics were down three games to one and facing elimination in that one before rallying to win the last three games and take the best-of-seven series, 4-3.

Anything can happen -- especially when it's these two teams facing each other in what has grown to legendary proportions over the years as one of the greatest rivalries in all of sports. But you never would have known that from the day-by-day reaction of fans on both sides this time around.

It started in Game 1, when Boston won by 40 points -- a humiliation from which almost everyone agreed that Philadelphia would never recover. So the 76ers came out and upset the favored Celtics at Boston Garden in Game 2, then won the next two at home to take a commanding 3-1 lead.

Now it was the Celtics who couldn't possibly win in the eyes of most observers. Oh, yes, they had come back from a similar deficit a year ago, but surely it was too much to expect any team to pull off a stunt like that twice in a row.

They did win Games 5 and 6, though -- the latter an 88-75 rout in Philadelphia during which the 76ers looked virtually helpless, scoring only 27 points in the entire second half, including an 11-point last period that tied the NBA record for fewest points in the final quarter of a playoff game.

So now, of course, the fair weather folks shifted bandwagons once again, voicing the near-unanimous opinion that it was all over for Philadelphia. After blowing their chance at home, the 76ers certainly had no hope playing the decisive game in the hostile environment of Boston Garden, with 15,000-plus fans urging their foes on from start to finish, and with all those banners hanging from the rafters to remind them of the Celtic tradition of success in such encounters.

''Will Sixers Choke?'' screamed the headline of one Boston paper as the teams returned to the Hub for Sunday's decisive game. ''Deja vu'' said a large banner hanging from the balcony across from their bench. And of course these sentiments referred not only to recent history, but to the long saga of Philadelphia frustration at the hands of Boston teams all the way back through the Bill Russell vs. Wilt Chamberlain era.

''Deja vu is a power forward from Paris,'' laughed 6 ft., 11 in. Philadelphia center Darryl Dawkins, but few people thought the 76ers would really be able to whistle their way around all those ''ghosts'' of basketball seasons past.

Then it was lesson time again. These are two outstanding teams that had battled through seven games a year ago, with Boston winning the finale by just one point, and here they were in a seventh game once again. Obviously there isn't very much to choose between them -- and when it all comes down to one game , everything can turn on who is hot or cold, who gets into foul trouble, etc.

Indeed, one writer listening to a group of people already consigning the 76 ers to oblivion before the opening tap-off noted that it all might depend on something as unpredictable as the shooting of Philadelphia's brilliant but erratic guard, Andrew Toney.

''You can pretty much assume that All-Stars like Julius Erving of Philadelphia and Larry Bird and Robert Parish of Boston will play their games and get their points,'' he said (they wound up with 29, 20, and 23 respectively). ''So a lot depends on whether Toney has one of his 39-point games (as in Game 4) or a three-point game (his total production in Game 6).''

Well, Toney came a lot closer to the former, leading all scorers in the finale with 34 points, and the 76ers rolled to a 120-106 victory to advance to the overall championship series against the Los Angeles Lakers starting Thursday night in Philadelphia.

It was a sweet victory indeed for the 76ers -- most especially, perhaps, for Erving, who has tried so valiantly to lead this team to the top ever since coming to Philadelphia from the then-New York Nets in a much-publicized transaction six years ago, and for Coach Billy Cunningham, who has certainly experienced more than his share of bitter moments in his five years at the helm.

''I just saw Billy, and he looked about 100 pounds lighter,'' joked Boston Coach Bill Fitch, who was as gracious in defeat as he had been in victory a year ago. ''I think I've got about 95 of them crawling up my back.''

Before all this levity, though, there was time for one more lesson. It came when the game was already hopeless for the Celtics; it dealt with things like sportsmanship and class; and it was given by the Boston fans.

The 76ers have had a succession of playoff failures in recent seasons, including two losses in the finals plus that humiliating experience of blowing a 3-1 lead to Boston a year ago. And the Philadelphia fans, never known for their patience or tolerance, have grown increasingly non-supportive of their heroes during this stretch. They reached perhaps the height of poor sportsmanship when the 76ers lost Game 6, heaping ridicule and jeers upon their own home team as it left the court.

But as the clock wound down in the finale, the players on both teams along with a national television audience got a demonstration of the way real sports fans show their appreciation for a hard-fought series - even when their team is on the losing end. Instead of turning sour, the disappointed Boston Garden fans stood and cheered their own players, then offered their encouragement to the victors, who will now carry the Eastern Conference banner into the final, with a chant of ''Beat LA!''

It was a stirring sight, a fitting conclusion to a great series, and a perfect reminder of what sport is really all about.