Last night there was a party at Lebanese Ambassador Khalil Itani's home in honor of His Beatitude, Antoine-Pierre Khoraiche, Maronite Patriarch of Antioch and all of the East, President of the Assembly of Catholic Patriarchs and Bishops in Lebanon. It's easiest just to call him His Beatitude.

Titles, however, didn't matter to some. Richard V. Allen, the president's national security adviser who has kept a lower-than-usual profile lately, stood talking to Bishop James Malone from Youngstown, Ohio. They just happened to have a friend in common, Charlie McCrudden from Notre Dame.

So they talked pleasantly about Charlie for a while. Then the bishop politely inquired of Allen:

"What do you do?"

"I work with the government," said Allen. "The United States government."

The bishop smiled. Several eavesdroppers chortled.

"These are Catholics," Allen explained to the eavesdroppers, "from the central part of the United States."

His Beatitude, or Khoraiche, was much more recognizable. "He's one of the few symbols of unity in Lebanon," said Arab League Ambassador Clovis Maksoud, one of some 500 people who filed into the house to make it as lively as it was before the 1975 Lebanese civil war.

The impetus was clearly Khoraiche, the popular and important religious figure in Lebanon. He not only leads the Maronite Church, Lebanon's dominant Christian order, but also serves as a moderating force between the Moslems and Christian factions. He is here for the National Conference of Catholic Bishops (the Maronites are an Eastern sect of the Catholic Church), and tomorrow is scheduled to talk with President Reagan about Lebanese strife.

"There are problems," he said last night, "but not religious problems." Khoraiche, like other Lebanese leaders, maintains that while the Lebanese war has religious overtones between Christians and Moslems, the real problem is the stateless Palestinians.

But the Lebanese pride themselves as a resilient people, and last night they proved it. The party was noisy, full of politicians, and had good food, even a whole lamb on the table that a waiter carved into bite-sized pieces. "They're not going to come in here and sit around and mourn about the country," said Rep. Toby Moffett (D-Conn.), who's of Lebanese descent.

Other guests included William Baroody, the president of the American Enterprise Institute, who's also of Lebanese descent. There were lots of Catholic bishops. They didn't talk about the reports that Chicago's Cardinal Cody funneled $1 million in church funds to a lifelong female friend -- unless they were asked by indelicate reporters.

"If there is sex involved," said one local priest who didn't want his name used, "while it certainly would be a surprise, I don't think people will judge anyone else by a single event. The benign people will understand it as a human weakness."