In 1966, Paul VI’s birth control commission presented its preliminary report to the pope. It held big news: The body had overwhelmingly voted to recommend lifting the prohibition on contraceptives. (The former Archbishop of Brussels, Cardinal Leo Suenens, went so far as to say the church needed to confront reality and avoid another “Galileo case.”)

Catholics rejoiced, and many began using the pill at once. But their hopes were dashed when, in July 1968, Paul VI released an encyclical titled Humanae Vitae (“on human life”), reaffirming the contraceptive ban. (He was two years to late.) It turned out that three dissenting bishops on the commission had privately gone to plead with the pope: If the position on contraceptives was changed, they said, the teaching authority of the church would be questioned—the faithful could no longer trust the hierarchy.

Ironically, it was the prohibition on contraception that would help erode the church’s power with European and American Catholics. Laypeople overwhelmingly disregarded it, and bishops throughout Europe undermined it with statements reassuring couples to “follow their consciences.” American bishops were more circumspect, but a survey of Catholic priests in the early ’70s showed that about 60 percent of them believed the prohibition was wrong. Father Andrew Greeley, a noted sociologist, traces the decline in church membership and even vocations to the priesthood in the mid-1970s to Catholics’ disillusionment with the church’s integrity on birth control.