On Monday, Pope Paul V1 celebrates his 80th birthday. Despite elaborate preparations in the Vatican and throughout the Catholic world to commemorate this event with joy, the Holy Father will probably go about his daily routine unperturbed.

In all likelihood he will merely acknowledge having joined the club of octogenarian pontiffs who have governed the church over the past century with the exceptions of Pius X, who died at 79 in 1914, and Benedict XV, who died at 69 in 1922.

What is remarkable about these long-lived popes is that nine died of lingering illness; almost all died literally with their papal slippers on.

In Pope Paul's case, several recent remarks in reference to his own demise as not too far distant have completely misinterpreted. His reflections are nothing more than the realistic sentiments of a pious Christian who at 18 or 80 suddenly recalls the mortality of all things human.

Physically, he suffers from a form of arthritis, which makes walking painful, and the other normal ills of a man of his age. But Pope Paul is totally alert and is abreast of events and trends that affect the church's and the world's well-being. He retires early, but takes with him into his bed-chamber an arm-load of daily newspapers from around the world.

Each week, he addresses thousands of pilgrims. In his discourses, he displays a remarkable attention to world events from the horrors of guerrilla warfare in Northern Ireland, Ethiopia, Lebanon and southern Africa to kidnapings in Germany and Italy, the outbreak of cholera in Lebanon and power failure in New York.

With an impossible act to follow - that of the portly Pope John with his genial countenance and impertubable good humor - Paul has not merely completed John's Council, but has helped to create a new self image of the church, its internal, discipline and structure, that even Pope John would have found revolutionary.

In the process, Paul has presided over a great blood-letting - the thousands of priests and nuns who have abandoned their vocations, the millions of Catholic who have simply ceased to function as the faithful. At the same time, however, he now has the church more committed to the Christian presence in the world than ever before in its 2000-year history.

Besides the audacity of his continent hopping as the jet age pontiff - Paul has voyaged to Jerusalem and Istanbul to support the position of the Orthodox patriarch, to Bogota in Latin America and Kampala in Africa, to India, the Philippines, Indonesia, Samoa and Australia - the pontiff has given official witness before the United Nations Assembly in New York that the Roman Catholic Church is an intimate member of this world's community, and means to make its presence felt. In so doing, his contribution to the world's well-being has been immense.

Following a policy dramatically opposed to that of the preconciliar church, he has opened dialogue with both the Communist bloc and the Third World countries. In so doing he has supported the principal objectives of the United Nations and UNESCO, condemned warfare outright with his impassioned cry, "War Never Again! No More War!" and showed a solicitude for the exploited and oppressed that is truly revolutionary.

His encyclical Progressio Populorum - On the Development of Peoples - is a text book for liberation from the shackles of oppression in all spheres of human interest, accompanied, however, with his own personal caution. "Violence is not in keeping with the Gospel."

As archbishop of Milan, long before becoming the supreme pontiff, Paul had earned the animosity of Spain's General Franco by appealing for the lives of condemned youthful anarchists. As pope, he masterminded the career of the present archbishop of Madrid. Vicente Cardinal Enriquey Tarancon, placing him in a position to aid King Carles in his introduction of a truly democratic regime in Spain.

For his support of nationalist aspirations in Portugese Africa he won the displeasure of Salazar; and despite the oppression of the church in Cuba, he has given subtle recognition to the struggle for social justice there by continuing diplomatic relations with the Castro government.

In the Philippines, Pope Paul gave the cardinal's hat to Archbishop Jaime Sin in order to give that prelate some standing in his opposition to the injustices of the Marcos government.

Paul's commitment to the vindication of human rights is absolute. Within the church, it was first indicated by the freedom of expression granted the prelates and theologians at Vatican Council 11. It was given full recognition with his abolition of the ancient Holy Office, the Inquisition and the Index of Forbidden Books on the day before the Council ended.

It is still apparent in the forbearance he has exorted in refusing to condemn the upstart Swiss theologian Hans Kung and the rebel French archbishop, Marcel Lefebvre. In each case, of course, there is also the prudential motive of not creating martyrs.

Paul's policy toward the Communist nations has gained him the opprobrium of not a few conservative Catholics. Completely reversing the condemnatory policies of his predecessors, including Pope John. Paul has welcomed into the Vatican the principal leaders of the Communist countries from ex-President Podgorny and Foreign Minister Andrei Gromyko of the Soviet Union, to Marshal Tito of Yugoslavia, as well as other Communist leaders of both the East and West, including Vietnam. His current efforts to open relations with Peking are far from subtle.

In his dealings with these atheistic, freedom-restricting regimes, he has a double objective - relieving the oppression of Christian and other religious bodies, and the authentic optimism of the true Christian hoping for conversion.

In the minds of many, both inside and outside the church, his condemnation of artificial birth control was a grave mistake for both papal teaching and papal authority. Outside the church, the encyclical Humanae Vitae gravely damaged his popularity. His stand against indiscriminate policies of population control, and his outright condemnation of abortion have given him the status of a Sign of Contradiction.

Nevertheless, benevolent critics are beginning to see papal policy based on an indisputable reverence for spiritual values as a FELIX CULPA - a happy fault - in the sense that it has given the population problem a prominence it would never have achieved without the fracas that accompanied Paul's Humanae Vitae in 1968.

Unquestionably, the anguish to Catholics caught in the dilemma between their need to limit the size of their families and the papal prohibition of artificial means has led to a considerable loss of membership in the church. At the same time, however, for those who stayed, it has occasioned a remarkable growth in a sense of personal responsibility in dealing with one's conscience, when conscience is in conflict with church teachings.

Catholic conditioned to follow, literally and without exception, the church's teachings now feel free to interpret their obedience in a much wider sense. The result has been an upsurge of a spiritual maturity among millions of concerned Catholics.

With his obvious unremittant attention to the things of eternity as they project into this world, Pope Paul has no intention of resigning at 80. That he has forced cardinals to cede their ecclesiastical offices and deprived them of the right to vote in a papal election on reaching their 80th birthday had no significance vis-a-vis the pope's concept of the papal office.

Cardinals are created by popes. But the pope's position is unique. He is elected, it is believed, with the concurrence of the Holy Spirit. As such, his position and status differ totally from that of the College of Cardinals whence he sprang.

What is obvious about Pope Paul at 80 is the vigor of his mind and the depth of his commitment to his task. Should he run true to form, death will catch him quickly, on the wing. But there is no indication that he intends to lay down the burden of office before receiving a definite call from eternity. In his make-up is an indelible devotion to biblical admonition: "Be you faithful until death!"