It may not be immediately clear what connection could possibly exist between a ban on artificial intelligence in the Dune universe and a letter by a Pope on contraception, but let me explain.
One of the founding myths of the universe of Dune by Frank Herbert is the
Butlerian Jihad
.
The Jihad was a conflict 10,000 years before the events of the novels whose effect was to ban the creation and use of artificial intelligences.
To replace the function of the banned "thinking machines", humans develop "human computers," known as Mentats, whose training, aided by the ingestion of "Sapho juice," allows them to exceed the performance of machines. Other orders of specialized humans also develop in the wake of the jihad.
Most notable is the Spacing Guild, whose members use of the drug "melange," a.k.a. "the spice," to safely navigate enormous starships through space. Similarly the Bene Gesserit order owes its superhuman powers to use of melange.
It is interesting that this novel, published in 1965, envisions a world built on the use of chemicals to make up for the loss of mechanical means.
In 1968, Pope Paul VI published the encyclical
Humane Vitae (On the Regulation of Birth)
. The encyclical was written in the wake of the availability of hormonal birth control pills starting around 1960. The basic argument against chemical contraception is that it is wrong to do anything to interfere with the natural ends of sexual intercourse. (Abstinence of course is a different matter, because abstaining from a good but not obligatory thing is not the same thing as doing a bad thing.1) Mechanical contraception, like condoms and diaphragms, had long been unacceptable for Catholics. So, starting in 1968 both mechanical and chemical interference were taught to be equally wrong.
One of the early developers of chemical contraception, Dr. John Rock, was in fact a Roman Catholic, and he had campaigned for the invention to be accepted by the Church. Once Humane Vitae was published, he withdrew from the Church in disappointment. I haven't read his 1963 book The Time Has Come: A Catholic Doctor's Proposals to End the Battle Over Birth Control justifying his position, but I found
this article that includes a summary:
In his book, Rock argues that since the pill functioned by suspending ovulation, it did not violate the Church’s edict that no one be permitted to deliberately suppress reproductive function. He contends that the rhythm method actually suppresses reproductive function, since by avoiding insemination the ovum cannot be fertilized; by contrast, if ovulation is suspended there is no egg to be fertilized, and he reasons that the contraceptive pill fulfilled the edict better than the rhythm method does.
Assuming his argument is conveyed fairly here, it is problematic in terms of any sort of traditional human morality. He seems to be focusing on the nature of the ovum (a part of a human), rather than the nature of the human persons, female and male, involved. It's kind of a crazy argument, in that it would seem to assume that it's somehow wrong to allow an ovum to go unfertilized, a position that if followed consistently would make women's lives (and secondarily those of their husbands) rather inconvenient! In reality it is not an ovum (or any human organ by itself) that exercises "reproductive functions" but whole organism, the human person, that does so, and the latter do right or wrong by respectively living or denying through their voluntary actions the nature that their Creator gave them.
To exercise will power in abstaining from intercourse for a good reason is an exercise of a natural human faculty that requires virtue and builds up and morally improves the human person. Avoiding conception in this case works with nature.
On the other hand, taking a chemical contraceptive, no less than employing a mechanical contraceptive, to block the natural purpose of sexual intercourse (the conception of children) is a violation of human nature. Using chemistry rather than mechanism to manipulate nature doesn't somehow make a violation good, but just as much degrades the humanity of the people involved.2 And that's not even mentioning all the evidence of the physiological harm of chemical contraceptives.
To bring this back to Dune, humanity turns to chemicals to augment human abilities that would have been exercised by machines. The idea is that we humans don't want to give machines control over us, but want to keep power in the hands of humans. But it's not clear that these chemically modified humans are entirely aligned with the interests of human beings in general. Indeed, the (Spacing) Guild navigators, whose bodies have been mutated by exposure to the spice, don't even look human any longer. An argument could be made that the intrigue of the competing interests of the Dune universe is largely due to the respective differences of the orders/guilds, whose post-human identities were delineated by chemical manipulation.
That argument could be made, but I think a more powerful argument is that the source of the strife in that world is the lack of a single, unified vision of what defines humanity, human nature, and thus human rights and responsibilities. So each faction of post-humans is striving for a disparate vision for the future of "all humanity." But ultimately the same post-Darwinian nominalism that denies a single human nature also fails to recognize how chemical interventions could spawn a new species... and indeed denies that "species" is even a coherent concept.
There's a sense that Frank Herbert's depiction of the strife in the Dune universe was a prophetic warning against the use of chemical interventions to attempt to preserve humanity, but it's also true that he himself succumbed to the conceptual errors behind that mistake in his portrayal of the possibilities of a post-human universe. John Rock was no less a victim of the reductive nominalism that has infected the cultural atmosphere in our modern age.
Notes
1. Oh and by the way, to bat down a common misconception: natural family planning (NFP) is not the same as the "rhythm method." The former takes its cues from physiological changes that signal the phase of a woman's cycle, while the latter is understandably ineffective because it simply counts the days under the assumption that all women have the same periodicity.
2. Will power works in and through human nature (the human being a whole: an embodied spirit or an ensouled body), whereas mechanical and chemical interventions insert themselves into nature from outside as it were. The latter treat the human body as if it were a machine to be manipulated at will, rather than a whole whose integrity needs to be respected.
