The two lines of thought, like the two subways lines that carried them, met at Grand Central Station last evening.

On the lower platform, dressed in blue and orange and emerging from the Flushing Local, were those who pledged their allegiance to the New York Mets.

On the upper platform, clad in navy pin stripes and bound for the Woodlawn train that would take them north into the Bronx badlands, were those with minds of a Yankee bent.

Those below had pledged their troth to knights like Dwight Gooden and Ron Darling, Jesse Orosco and Sid Fernandez, Keith Hernandez and Gary Carter, George Foster and Darryl Strawberry.

Those above had no use for such unworthies. For them, Ron Guidry and Phil Niekro, Dave Righetti and Rickey Henderson, Don Baylor and Dave Winfield, Willie Randolph and Don Mattingly were the proper men to hold in thrall.

For nearly a quarter of a century, since the New York Mets came into being in 1961, these two New York breeds of baseball fan have seldom, and only with trepidation, crossed paths.

Yankee fans have taken the high road of tradition and haughty contempt, while Metsomaniacs have cheered along their populist low road.

Never have the teams met in the World Series and not until this season have they both been engaged in legitimate pennant races at the same time.

Yet today, by a confluence of luck that even New Yorkers, who believe the world revolves around them, find wonderful, both teams not only played on the same day but played against their chief rivals.

Baseball has seen plenty of doubleheaders but none, perhaps, like this intra-metropolis extravaganza.

The Mets and the St. Louis Cardinals, tied for first place in the National League East after 137 games, met at 1:35 at Shea Stadium under bright skies and raucous jets. The Mets won a corny and marvelous thriller, 7-6, in 10 innings after squandering a 6-0 lead.

Just 90 cents and 55 minutes away by subway, or $25 and 2 hours (minimum) by taxi, the Yankees and the first-place Toronto Blue Jays, separated by just 2 1/2 games in the American League East, met at 8:05 under crisp World Series weather conditions.

Yes, the only four teams in the game with winning percenatges over .600 were playing in the same town on the same day. It may have happened before. It's just that nobody can remember when. The last Subway World Series was a generation ago, in 1956 between the Yankees and Brooklyn Dodgers.

As sundown approached, the habitues of the No. 7 IRT from Shea Stadium and the No. 4 IRT to Yankee Stadium crossed paths. Or, as one Yankees fan bellowed when a half-dozen Mets-hatted men got off at the 161st Street station in the Bronx, "Get them Mets hats off."

T-shirts already are being sold here that say, "New York Wants a Subway Series."

Fascinating as that would be, this day hardly seemed a harbinger of such October madness. True, all those symbols of New York City intimidation awaited the visitors. One brawl in the left-field corner at Shea lasted longer and drew a bigger crowd, than some of heavyweight champion Larry Holmes' recent fights. When the polite Blue Jays arrived for batting practice, they were greeted with the same obscene chants that the Boston Red Sox learned to know and dread in the late 1970s.

Even Canada's lovely national athem wasn't safe. Who'd boo "Oh, Canada"? Well, a near-capacity crowd at Yankee Stadium would. Front to back. And with certified New Yorker Robert Merrill at the larynx.

The Mets-Cardinals three-game series, which ended yesterday, gave as much solace to St. Louis, which lost the first and last games (5-4 and 7-6) as it did to the Mets (who lost the middle masterpiece, 1-0, in 10 innings.)

"This is as tough a series as I've ever been involved with," said Keith Hernandez, whose one-out, sudden-death opposite-field single at 4:54 p.m. sent the huge Shea crowd toward the parking lots and elevated train tracks.

"It's a big win for our club. If they come back from 0-6, it might have given them momentum that would have carried them who knows how long. It'd certainly have tested our character.

"They'll move on to the next town and battle," added Hernandez. "I can see this going down to the wire. I hope we don't have to go to St. Louis (for three games the last week of the season) to tie it up."

This is extremely tentative talk from a very confident and seasoned player. What lurks behind the words, perhaps, is the unspoken assumption that the Cardinals, as soon as they get cleanup man Jack Clark back, are the better team. Certainly, the Cardinals have the easier schedule (13 of their last 16 games at home) and the calmer manager.

St. Louis skipper Whitey Herzog almost seemed bored by the day's proceedings. "I was thinking about taking my regulars out if they got a couple of more runs early," he said. "One game don't mean much."

One game Herzog did think was important, and very much wanted to see, was this evening's shindig at Babe Ruth's House. "Boys, I'd sure like to be there," he said, "but I gotta get my fanny movin' to Chicago."

In contrast to the Cardinals' toughness, even in defeat, the Blue Jays seemed a bit like tender meat being brought to the Yankees' banquet board. The Bronx Bombers, possessed of one of the sport's most potent lineups in 30 years, had won 30 of 35 games and had cut what was once a 9 1/2-game Toronto lead to just 2 1/2 games.

The Jays got the best of the early going, building a 4-1 lead against Ron Guidry. In the fourth, Winfield foolishly tried to stretch for a double. A fabulous throw by George Bell both embarrassed Winfield and counterpointed a pathetic rainbow overthrow to the plate by the Yankees' Henderson in the top of the inning.

No sooner had the Yankees finished their futile inning than the huge stadium message sign flashed an advertisement with Winfield intoning, "This is Dave Winfield and this is Yankee baseball."

Such groaners have precedent. In the third quarter of the most famous slaughter in football history -- the Chicago Bears' 73-0 win over Washington in an NFL championship game -- the public address system informed the crowd that "Redskins season tickets for next year are now on sale."

Baseball, however, is a game rich in atonements. Especially against a team like the Blue Jays that never has been exposed to maximum pressure. In a six-run seventh, Toronto came unglued.

Tony Fernandez, the Blue Jays' prize rookie shortstop, got the jitters and flipped away a perfect inning-ending double play ball with a toss to nobody. Pitching ace Dave Stieb got the hot collar and the cold shower. And Toronto Manager Bobby Cox, in his first pressure cooker, called for his fourth-best reliever, Dennis Lamp, with all of Yankee Stadium howling for blood.

Just like it says in the How Not To Manage In A Pennant Race night-school manual, Lamp gave up a game-tying hit to Winfield and a gargantuan upper-deck, three-run home run to Ron Hassey.

As Hassey's rocket headed toward Flushing, folks in the Big Apple could go to sleep savoring a tiny Mets lead and a tiny lump in Toronto's throat. Whether both would grow, no one knew. But for aficionados of the IRT, it was the perfect ending to a unique day.