...is the “slippery slope”.
In 1968 Pope Pius VI wrote Humanae Vitae (On Human Life) in direct
response to world-wide pressure to stop opposing contraception. A lot
was going on in the late '60s from the creation of the birth control
pill to Vatican II. The world waited expectantly as the last bastion
against “women's freedom” looked like it was finally
going to fall. To say Humanae Vitae was a disappointment to those
seeking the Church to change would be quite the understatement.
Far from simply reiterating the Church's position, Humanae Vitae was,
and probably still is, the most articulate explanation of the Church's
views ever written. Part of the document's emphasis is on the secondary
effects of a society that embraces contraception. Among them are
opening the way to marital infidelity, men forgetting “reverence due to a
woman” by “reducing her to being a mere instrument for the satisfaction
of his own desires”, governments would force its use on unwilling
recipients, and that humanity would come to believe the human body is
under his authority, not God's.
Increases in marital infidelity
isn't s shot to anyone and the cause is clear. Too bad King David
didn't have a condom; he may not have had to murder Uriah after getting
his wife pregnant.
Reducing women to instruments of satisfying desires is equally obvious. Pornography is now the #1 cause of divorce.
Government manipulation is terrifying to behold when we look to China's
One Child policy. There have been cases of forced abortion in the U.S.
Where judges rule pregnant, mentally handicapped women must abort their
child (below for source).
Finally, humanity's view of
ownership of our bodies has a natural conclusion as well. If “my” body
is pregnant and I don't want it to be then I should have the right to
fix that. If my body truly is under my authority then it makes sense
that I can remove a fetus if I don't want it there. If my body is only a
gift and it truly belongs to God (not even to mention the unborn child)
then I do not have authority to abort.
That contraception leads to more and more morally objectionable behavior is yet another reason why Catholics reject it.