To some the ban on artificial contraception seems logically inconsistent why is it all right to prevent conception naturally, but not artificially, if sin consists of intent, and not outcome?
Since it took until 1992 for the Vatican to admit it was wrong to condemn Galileo, Mr Stourton is not sanguine about early recantation on the ban on artificial contraception, which has lost the church millions of adherents and left millions more forced to make agonising choices between misery and sin.
But in parts of the developing world, where Catholic agencies are at the forefront of health provision, the stricture against condoms condemns women to years of child-bearing, and encourages the spread of HIV, the precursor to AIDS. Some women are as strongly opposed to the church's ban on abortion as they are on its stance on contraception.