They can steer in directions not widely anticipated. A half century ago, it seemed the world was moving toward ever more collectivism and centralization, toward ever greater secularism and skepticism: This was modernity, and Marx and Freud were its prophets. Experts at the top of hierarchical pyramids would determine the course of events. Authoritarian and totalitarian regimes ruled most of the world's people, and in an age of nuclear weapons, no one could hope to change that. The best that could be wished for was a convergence of systems.

 Karol Wojtyla thought something different. He was 19 when Nazi Germany overran his native Poland; through World War II he worked in a quarry and acted in clandestine illegal plays. He sheltered Jews and was once arrested by the Gestapo. Then, after the Red Army swept into Poland and installed a Communist government, he attended seminary and became a priest, a bishop and an archbishop. In the pulpit and out he called for religious freedom and freedom of conscience, implicitly rebuked a regime built on lies. Today, we can read about the millions of people murdered by Hitler and Stalin. Pope John Paul II lived under their rule, but kept his own mind and conscience free.

 In 1978, when he was 58, Karol Wojtyla was elected pope; he had lived most of his life under totalitarian governance. This was the same year in which Juan Carlos I, groomed to be King of Spain by the dictator Franco, presided over free elections in Spain -- a transition to democracy that, as Michael Ledeen has written, inspired similar transitions in other parts of southern Europe and Latin America. And it was the same year that Ronald Reagan, past retirement age, was writing radio commentaries and preparing to run for the third time for president of the United States. This time he would win, and would put in place policies that did much to end the Soviet Union and the Communist regimes it supported. 

 The next year, the Pope returned to his native Poland and appeared before crowds of 1 million in Warsaw and Gniezno and Czestochowa. Thirteen million Poles -- one-third of the nation's population -- saw the Polish Pope in person. He spoke words of hope and faith, and without openly advocating the overthrow of the Communist regime made it clear that it did not hold the people's allegiance. As his biographer George Weigel wrote, "A revolution of the spirit had been unleashed." For much of the 19th and early 20th centuries the Catholic Church had looked askance at democracies and had seen authoritarian regimes as upholders of the faith. Pope John Paul II heartily embraced representative democracy and enunciated a sophisticated appreciation of free markets and their limits. He engaged in serious moral dialogue and presented a vision of modernity different from that of the disciples of Marx and Freud.

Would the Solidarity movement that undermined the Communist regime in Poland have emerged with the courage and hope it did without Pope John Paul II? Would the Soviet Union have lost its Eastern European satellites and its very existence without the Pope and Ronald Reagan? Would Spain have made the transition to demcracy and freedom and set the example it did without King Juan Carlos I? We cannot be certain of the answers to these counterfactual questions. But it seems as certain as such things can be that different leaders would have produced different, and less happy, results. Juan Carlos lives today the routine life of a constitutional monarch; Ronald Reagan withdrew from public view as Alzheimer's clouded his vision; John Paul II, his body wracked with Parkinson's, struggled to do his duty until the end. This man who lived under Hitler and Stalin, like the American president and the Spanish king, steered history in a surprising and felicitous direction, a direction unforeseen a half century ago.

Michael Barone is a senior writer for U.S.News & World Report and principal coauthor of The Almanac of American Politics.