Scientism or the "Church of Science" is a fictional religion from Isaac Asimov's Foundation series. It is first mentioned in Part III of Foundation, "The Mayors", and makes its last appearance in Part V, "The Merchant Princes".
The Foundation, a large colony of scientists on the planet Terminus, find themselves cut off from their supporters in the Galactic Empire and threatened by the newly-independent neighboring Kingdom of Anacreon, which covets their possession of scientific knowledge and nuclear power. The leader of Terminus, Mayor Salvor Hardin, visits three other nearby kingdoms and convinces their leaders that allowing Anacreon to conquer Terminus would make that kingdom powerful enough to conquer them in turn. The three other kingdoms force Anacreon to back down.
Hardin goes on to offer scientific and medical assistance to all four kingdoms, reasoning that this will make them less likely to join together for a combined assault on Terminus. The barbarized inhabitants of the four kingdoms believe that the Foundation's technicians are magicians. Being unable to make these people understand the difference between magic and science, the technicians finally give up and allow themselves to be worshipped as holy men. Back on Terminus, Hardin accepts the situation, and organizes the Foundation's technical assistance program as a religion. The technicians are organized into a priesthood, and the Foundation's ambassador to each kingdom becomes the High Priest, with Hardin himself assuming the role of Chief Primate of the whole religion.
The resulting religion is never given a formal name in the novel, but it is referred to several times as the "religion of science", hence the name "Scientism".
In addition to the technician-priests (an atomic priesthood that controls the technology of nuclear power) from Terminus who travel to the worlds of the Four Kingdoms, the church also recruits priests from among the native populations of those worlds. They travel to a Temple School in Terminus City, where they are taught the operation (though not the theoretical underpinnings) of the Foundation's technology, along with more traditional religious instruction in church dogma, theology and ethics. Any novitiate priest at the Temple School who is bright enough to see through the mystical surface to the scientific principles underneath remains on Terminus to become a research student. The rest return to the Four Kingdoms to form part of the priesthood.
As a character in "The Mayors" notes, the priesthood is built on strictly authoritarian lines, forming a hierarchy with the king (who is regarded as a minor god) at the apex. The priesthood is in charge of all technology in the Four Kingdoms, including hospitals, power plants, and military installations (it is mentioned that the navy yards on Anacreon are religious sanctuaries completely inviolate on the part of the lay public). Every ship in the Four Kingdoms' space fleets is assigned a complement of Foundation-educated priest-attendants to maintain the technology as well as provide spiritual guidance to the crew.
There is mention made of an ecclesiastical court, implying that members of the priesthood are beyond the reach of whatever secular justice system exists in the Four Kingdoms. The ecclesiastical court is also empowered to try laymen for violations of church law (in "The Mayors" the head priest-attendant of the Anacreonian Navy orders the king's cousin, Admiral Lefkin, tried before an ecclesiastical court for blasphemy).
The Church of Science also includes a missionary organization whose purpose is to spread the Church's spiritual dominion (and hence the Foundation's political control) to other worlds. However, Hober Mallow remarks in "The Merchant Princes" that "however well your religion has succeeded in the Four Kingdoms, scarcely another world in the Periphery has accepted it." One of the exceptions to Mallow's remark is the planet Askone, and as revealed in Part IV of Foundation, "The Traders", Askone was first brought within the Foundation's orbit by a trader, with the priesthood only following on afterwards.
When he is asked what kind of religion Scientism is, Lewis Bort, a character in "The Mayors", states that "Ethically, it's fine. It scarcely varies from the various philosophies of the old Empire. High moral standards and all that. There's nothing to complain about from that viewpoint."
From remarks made by various characters, it is apparent that the Church of Science teaches that spiritual rule of the Galaxy is held by the Galactic Spirit, though there is no mention made as to whether the Galactic Spirit is credited with creating the universe. The priesthood is taught that the Galactic Spirit guides the operation of the Foundation's technology. Hari Seldon, the founder of the Foundation, is regarded as the Prophet of the Galactic Spirit, and the people of the Foundation were chosen by Seldon to carry on his commandments, that there might one day be a return of the Galactic Paradise (the future Second Galactic Empire predicted by Seldon). Though it is not specifically stated, Salvor Hardin, as Chief Primate of the Church, is presumably regarded as Seldon's successor as Prophet of the Galactic Spirit. It is stated, though, that anyone who disobeys Seldon's commandments will be destroyed for eternity. The high priest-attendant Theo Aporat declares that engaging in sacrilege will doom a person's soul to the eternal frigidity of space. Mention is made in "The Traders" of a Book of the Spirit, presumably a codification of the Church's teachings.
The power of Scientism's pronouncements is greatly enhanced by the fact that its rituals and observances are powered by technology and science, and therefore its clergy can reliably produce "miracles" on demand: the "Holy Food" is actually medicine, so it really does cure the sick; the throne of the King of Anacreon is really a flying machine, so he can truly levitate over his subjects with a glowing aura. So deep is the indoctrination of the priesthood that they continue to believe in the miracles, even as they themselves work the technology to make them happen. Most significantly, Scientism can follow through on its threats when the people offend the Galactic Spirit, casting the navy adrift and shutting down the entire planet except for the temples, with a word from a priest.
A hundred years after its establishment, Scientism has lost its utility as an instrument for the extension of the Foundation's political power. No world will allow Church missionaries to come and proselytize, and this in turn limits the worlds open to the Foundation's traders, who customarily encourage the priesthood to follow in their train.
In "The Merchant Princes", a Master Trader named Hober Mallow realizes that the power of religion is played out. Upon his election as Mayor of the Foundation, Mallow assumes the position of Chief Primate as well, the first man to hold both offices since Hardin. Mallow ends the policy of combining economic control with religious control, and encourages the Foundation's traders to sell their wares without bothering to help establish a priesthood.
The wisdom of Mallow's policy is demonstrated when the Republic of Korell declares war on the Foundation. Mallow had previously sold a vast array of nuclear-powered devices to the Korellians without bothering to establish a priestly hierarchy to control them. The Korellians had assumed that this left them free to conquer the Foundation, but they discovered that they still needed Foundation technical assistance to maintain the Foundation's technology. Once the Foundation-made goods begin failing, the Korellians find their industrial economy collapsing. Unable to carry on the war, the Korellians surrender to the Foundation.
There is no further mention made of the Church of Science in subsequent stories. Whether the Church has died out, or whether it continues to be the chief religion of the four kingdoms, is never made clear. It is even possible that with the end of the Foundation's policy of religious control, the restrictions against missionary activity by the Church have been removed, and that the Church continues to spread among the worlds of the Galaxy, ignored by the leaders of the Foundation.