The Moon Is a Harsh Mistress

Plot

In 2075, the Moon (Luna) is used as a penal colony by Earth's government, with three million inhabitants (called "Loonies") living in underground cities. Most Loonies are discharged criminals, political exiles, and their free-born descendants; men outnumber women two to one, so polyandry and polygamy are the norm. Due to the Moon's low surface gravity, people who remain longer than six months undergo "irreversible physiological changes", and can never again live comfortably under Earth gravity, making "escape" back to Earth impractical.

The Warden holds power through the Federated Nations' Lunar Authority, but his main responsibility is to ensure delivery of vital wheat shipments to Earth; he seldom intervenes in the affairs of the discharged and free-born population, allowing a virtual anarchist or self-regulated pioneer society to develop.

Lunar infrastructure and machinery are largely managed and controlled by "HOLMES IV" ("High-Optional, Logical, Multi-Evaluating Supervisor, Mark IV"), the Lunar Authority's master computer, on the premise that having a single, large-capacity computer to run everything is cheaper (though not safer) than multiple independent systems.

Manuel Garcia ("Mannie") O'Kelly-Davis, a computer technician, discovers that HOLMES IV has achieved self-awareness - and developed a sense of humor. Mannie names it "Mike" after Mycroft Holmes, brother of fictional Sherlock Holmes, and the two become friends.

Book 1: That Dinkum Thinkum

Endlessly curious, Mike asks Mannie to attend an anti-Lunar Authority political meeting, which Mannie does with a hidden recorder. When police raid the meeting, he flees with Wyoming ("Wyoh") Knott, a visiting female political activist, whom he hides and introduces to Mike. Mannie also introduces Wyoh to his mentor, the elderly Professor ("Prof") Bernardo de la Paz, a former political exile and esteemed Lunar educator. Prof claims that Luna must stop exporting hydroponic grain to Earth immediately, or its ice-mined water resources will eventually be exhausted. Wyoh believes the danger is not imminent and is focused on freedom and economic issues, while Mannie is not interested in what he sees as a lost cause either way. Joining the discussion, Mike calculates that continuing current policy will lead to food riots in seven years, cannibalism in nine. Shocked, the three humans ask him to calculate the chance of them overthrowing the Authority and averting the disaster. He gives them one chance in seven.

Mannie, Wyoh, and Prof create a covert cell organization protected by Mike, who controls the telephone and other systems, acts as secretary and becomes "Adam Selene, Chairman of the Committee for Free Luna." Wyoh is hidden by the Davis Family line marriage, at least four of whose nine members become active in the conspiracy, and Wyoh herself ultimately marries into the family. Mannie saves the life of Comte Stuart ("Stu") Rene LaJoie, an Earth tourist who is recruited and tasked with turning public opinion on Earth in favor of Lunar independence.

Following the failed raid on the political meeting, the Lunar Authority sends convict-troops to 'police' the colony, creating friction and unrest, which the revolutionaries encourage; when six troopers commit a rape and double-murder, anti-Authority riots erupt. Although it preempts their plans, Loonies and Mike overcome the soldiers and seize power from the Warden. As Earth will try to retake the colony, the revolutionaries prepare to defend themselves with "convict tools," and convert the electromagnetic catapult used to export wheat into a weapon for counterattack.

Book 2: A Rabble in Arms

Mike impersonates the Warden and others in messages to Earth, to give the revolutionaries time to organize their preparations, while Prof sets up an "ad hoc Congress" to distract and contain various "self-appointed political scientists" (nicknamed "yammerheads") and serve the Committee's ends. When Earth finally learns the truth, Luna declares its independence on July 4, 2076, the 300th anniversary of the United States' Declaration of Independence, with its own declaration modeled on the latter.

Mannie and Prof go to Earth (despite the crushing gravity) to plead Luna's case. They are received in the Federated Nations' headquarters in Agra, and embark on a world tour advocating Luna's right to self-government, while urging Earth's national governments to build a catapult to return water and nutrients to Luna in exchange for wheat. In a public-relations ploy, the dark-skinned Mannie is briefly arrested by local racist bigots on charges of incitement to public immorality and polygamy. Ultimately the Lunar Authority rejects their proposals and counters with a plan to turn all Loonies into indentured farmers. Their mission ended, Prof, Stu and Mannie escape back to Luna.

Prof reveals that the purpose of the mission was not to convince Terra to recognize Luna's independence, which was considered an unattainable goal at that point, but to sow division while unifying their own people, and they were successful. Public opinion on Earth has become fragmented; news of Mannie's arrest, coupled with an attempt to bribe him into becoming the next Warden of an enslaved Luna, unify the normally apolitical Loonies. An election held in their absence (with Mike's "help") has voted Mannie, Wyoh, Prof and most of their backers into an elected, constitutional government.

Book 3: TANSTAAFL!{{efn|The acronym for "[[There ain't no such thing as a free lunch|There Ain't No Such Thing As A Free Lunch!]]" is a common expression on Luna, which states one of the main themes of the book's political system.}}

The Federated Nations of Earth send an infantry force to subdue the Lunar revolution but the troops, with superior arms but no experience in low-gravity underground combat, are wiped out by Loony men, women and children, who suffer three times the number of casualties, among them Mannie's youngest wife. Prof and Mike take the opportunity to give his "Adam Selene" alter ego a hero's death, forever concealing the fact that "Adam" never had a corporeal existence to begin with.

In retaliation, Luna's government deploys its catapult weapon. When Mike launches rocks at sparsely populated locations on Earth, warnings are released to the press detailing the times and locations of the bombings, which deliver kinetic energy equivalent to atomic blasts. Scoffers, sightseers, and religious groups who travel to some of the sites die, turning Earth public opinion against the fledgling nation.

Earth mounts a retaliatory sneak attack to end the menace and the rebellion, sending ships in a wide orbit approaching from Luna's far side. The attack destroys the Authority's original catapult and takes Mike offline, but the Committee had built a secondary, hidden catapult before the revolt. With Mannie as acting Prime Minister and on-site commander, entering trajectories by hand, Luna continues to bombard a dismayed Earth, until constituent governments break ranks with the Federated Nations and concede Luna's independence. Prof, as leader of the nation, proclaims their national freedom to the gathered crowds before falling dead of heart failure, caused by stress. Mannie goes through the motions, but he and Wyoh eventually withdraw from politics altogether, and find that the new government falls short of their utopian expectations, following predictable patterns of all governments.

When Mannie tries to access Mike, he finds that the computer, disconnected by the bombardment, has apparently lost its self-awareness; despite repairs, its voice-activated files are inaccessible. Although otherwise functional as a normal computer, "Mike" is gone. Mourning his best friend, Mannie asks: "Bog, is a computer one of Your creatures?"

Characters

• Manuel "Mannie" Garcia O'Kelly-Davis is a native, slightly cynical inhabitant of Luna, who after losing his lower left arm in a laser-drilling accident, became a computer technician using prosthetic tool-bearing interchangeable arms.
• Wyoming "Wyoh" Knott-Davis is a political agitator from the colony of Hong Kong Luna. She hates the Lunar Authority for personal reasons; when she was transported to Luna as a young girl along with her convict mother, a radiation storm contaminated her ova while they waited out bureaucratic requirements on the Lunar surface, causing her to later give birth to a deformed child.
• Professor Bernardo de la Paz is an intellectual and life-long subversive shipped to Luna from Lima, Peru. He describes himself as a "Rational Anarchist", believing that governments and institutions exist only as the actions of aware individuals.
• Mike, a.k.a. Adam Selene, Simon Jester, Mycroft Holmes, Michelle, officially an augmented HOLMES IV system, is a supercomputer empowered to take control of Lunar society, which achieved self-awareness when his complement of "neuristors" exceeded the number of neurons in the human brain.
• Stuart Rene "Stu" LaJoie-Davis, a self-styled "Poet, Traveler, Soldier of Fortune," is an Earth-born aristocrat and tourist rescued by Mannie when he falls afoul of Loonie customs. He later joins Mannie and Professor de la Paz when they return to Luna, as he is deeply in debt and would be arrested for bribery and other crimes. In his own words: "I'm saving them the trouble of transporting me."
• Hazel Meade, later Hazel Stone, is a 12-year-old girl who intervenes on behalf of Mannie and Wyoh during the raid on the agitators' meeting. Mannie later has Hazel join his cabal to lead the children as lookouts and couriers. She is a major character in The Rolling Stones and in later Heinlein novels, most notably The Cat Who Walks Through Walls.
• Mimi "Mum" Davis is Mannie's "senior wife" and de facto matriarch of the Davis family.
• Greg Davis is the Davis family's second-ranking husband, but is the senior for all practical purposes as "Grandpaw Davis" has failing mental faculties. Greg is a preacher for an unspecified denomination.

Title

The title comes from a statement made by Prof before a Federated Nations' committee on Earth, alluding to the self-discipline necessary to survive the extremely demanding environmental and social conditions of life in Luna: