From the New York Times obituary of Cardinal Avery Dulles:
His spiritual passage to Catholicism was like a fable. A young scholar with a searching mind, he stirred from his establishment Presbyterian family to face questions of faith and dogma. By the time he entered Harvard in 1936, he was an agnostic.
In his second book, “A Testimonial to Grace,” a 1946 account of his conversion, Cardinal Dulles said his doubts about God on entering Harvard were not diminished by his studies of medieval art, philosophy and theology. But on a gray February day in 1939, strolling along the Charles River in Cambridge, he saw a tree in bud and experienced a profound moment.
“The thought came to me suddenly, with all the strength and novelty of a revelation, that these little buds in their innocence and meekness followed a rule, a law of which I as yet knew nothing,” he wrote. “That night, for the first time in years, I prayed.”
His conversion in 1940, the year he graduated from Harvard, shocked his family and friends, he said, but he called it the best and most important decision of his life.