The Eleventh Commandment

As the Supreme Court was considering if the 10 Commandments were appropriate decoration in public schools in the '60s, sf writer & history professor Lester del Rey was pondering what might be the result of established state religion. He set the stage for such in The 11th Commandment.
Following a nuclear exchange which destroyed the Vatican, a new pontiff was elected by American Cardinals. When Europe also elected a Pope, Americans split from the Old World in a schism establishing the priority of an 11th commandment: "Ten were given to Moses, for the Hebrews, & our Lord instrusted us to observe them. But what we call the 11th—it should be called the Original—was given by God the Father to the entire human race thru Adam, to whom He said, 'Be fruitful & multiply & replenish the earth.' It was the foundation of our accomplishments."
These principles found fertile ground in a decimated land. To Boyd Jensen, Mars colony immigrant, the culture is frightening. Four billion live in N. America, a billion in S. America. Most are American Catholic. Contraception is illegal. Boyd's profession, biologic research, is restricted to priests. Poverty is commonplace among the laity, practically unknown in the clergy. In addition to mass misery, mutations & plagues are everywhere. Boyd learns he'a not allowed to return to Mars, as he's been exposed to Earth diseases. There's a hint his DNA is damaged, that he was tricked into coming to Earth to remove him from Mars' gene pool.
Boyd believes he'll survive without subscribing to the state religion. He wears an unobtrusive patch to keep him sterile; he isn't the type to succumb to the bleeding disease; he's more valuable training in cytology than many priests. He hasn't reckoned with two things, however. 1st, at a higher gravity than Mars', the contraceptive is ineffective. Boyd impregnates a woman. Her baby is taken by the Church to be raised in a special facility. Boyd is determined to help rescue it. 2nd, the Church knows more than admitted about the extent of the mutations. The 11th Commandment may be the only thing guaranteeing human survival.
Del Rey's conception of a Catholic America is predicated on the 3rd world. Long Island seems like Caracas or São Paulo. He seems to suggest Catholicism causes poverty & overcrowding. Reading on, however, his message comes clear: The root cause of this misery is the need to contend for survival. You don't get to opt out of the game, as Mars has done with her pure racial stock. The crucible is where the metal is purified & made strong, not the shelf.
The 11th Commandment seems hardly dated. Its plot needs little amendment to be conceivable as a possible future. The warning that the fruitful will multiply & the meek inherit the Earth, is worth considering.