In my opinion, Lester del Rey is the most underrated (and under-read) founder of contemporary American science fiction. He is far better known as an editor than as a writer, but his stories are creative and his writing is very tight, and he routinely combines politics with personal stories in ways that are insightful and entertaining.

The Eleventh Commandment is set on a post-apocalyptic earth. After an accidental nuclear war, the American Eclectic Catholic Church (AEC) was the strongest organization remaining, and it seized both political and religious power in North and South America. A prominent cardinal notes that while the constitution of the United States declares that “congress shall make no law respecting an establishment of religion,” the reverse is not true: nothing prevents the church from supporting or dominating the state (the logic may be flawed but what theocratic state doesn’t have that problem?). And the church does dominate society and politics, particularly in the realms of science, technology and medicine.

The earth’s population is over 15 billion, and daily survival is a struggle, even for the wealthiest. There are some political differences between the AEC and the Roman Catholic Church (which dominates Europe), but the main doctrinal difference is the Eleventh Commandment – the AEC elevates god’s commandment to Adam and Eve – “be fruitful and multiply” – to the same level as the other ten commandments. Not only are abortion and contraception outlawed, but the lack of children is seen as a serious moral and social failing. A woman without children, especially a married woman without children, is not only failing to fulfill her duty to god, she is also failing to fulfill her duty to the state. And population pressures mean nothing to those in power. The AEC actively promotes continued population growth, no matter how bad local conditions become.

Into this complex mix of politics and religion comes a confused Martian. Before the nuclear war, Earth colonized the moon and Mars, and just after the war, Mars skimmed off the cream of Earth’s remaining intellects before cutting off further emigration. Leaders on Mars went to great lengths to protect their genetic purity by carefully screening all immigrants. Boyd Jensen, the grandson of one of the last immigrants, is thirty years old, and due to an extended illness is too “old” to continue his education on Mars. He agrees to participate in a student “exchange” program. He travels to Earth to continue his education, in the hopes of then returning to Mars triumphant.

After his arrival on Earth, Boyd learns that Mars didn't really intend for him to return. The story then becomes much like Voltaire’s Candide – Boyd travels the North American Continent and asks questions, and various people explain their philosophies and lives to Boyd. However, the story is never aimless like Candide, and the political story continues to build throughout.

The ending is satisfying although a bit abrupt, and like most SF authors of his era, Del Rey’s female characters are ill-defined and plastic. However, Boyd is a likable if unlikely hero and the ending is entirely consistent with what the reader learns from Boyd’s wanderings. There are no loose ends. The book is currently out of print, but should be easy to find in used books stores.