Paul VI proclaimed the encyclical Humanae Vitae banning artificial contraception in 1968. He did not issue any other encyclicals in the following ten years of his pontificate. It was as if he knew that what he had "infallibly" asserted was considered by the vast majority of Catholics to be manifestly fallible.
"For man cannot attain that true happiness for which he yearns with all the strength of his spirit, unless he keeps the laws which the Most High God has engraved in his very nature," wrote Paul VI.
By interpreting our God-engraved human nature as intrinsically heterosexual and procreative, the Church certainly did not increase the store of human happiness.
Where do we discover the God-engraved plan? In revelation. In the teaching authority of the Church.
But what about science, the most successful way humans have yet devised to discern the "laws of nature"? Paul VI had a role for science too.
Scientists can serve marriage and the family and also their own peace of conscience by pooling their efforts to elucidate more thoroughly the conditions favorable to "a proper regulation of births." In other words: I got rhythm. Who could ask for anything more?
All of this would be irrelevant if it were not for the fact that official Church policy has unfortunate consequences in places like Africa where sexually transmitted diseases are endemic. Even in the United States, as we have seen in recent weeks, bishops who are hopelessly out of sync with their flocks inject natural law into the political process, and a major presidential candidate invokes Catholic natural law tradition to support ultra-conservative social policies.
But back to Humanae Vitae. Paul VI writes: "The most remarkable development of all is to be seen in man's stupendous progress in the domination and rational organization of the forces of nature to the point that he is endeavoring to extend this control over every aspect of his own life -- over his body, over his mind and emotions, over his social life, and even over the laws that regulate the transmission of life."
In this, of course, he is surely correct. The stupendous progress of which he spoke has flowed from an understanding of natural laws determined empirically, not from revelation or tradition. The powers we now have over our bodies, minds and social lives are indeed awesome. Exercising those powers wisely is our collective challenge -- liberals, conservatives, religious and secular. In this the Church might pay more attention to the sensus fidelium (sense of the faithful), and less to the pre-scientific speculations of 13th century philosophers and theologians.