I re-read Moon is a Harsh Mistress over the weekend and remembered that I was always puzzled by Mike's behavior over the last pages.

Prior to Prof's death, Mike was both a friend to Man and Wyoh as well as playing the roles of Adam Selene and Simon Jester. After Prof dies, Man wonders if

... a machine be so frightened and hurt that it will go into catatonia and refuse to respond? While ego crouches inside, aware but never willing to risk it?

Man also came up with two possibilities. The first is that Mike took enough damage to fall below the critical number required to sustain self-awareness, and the second is implied that Mike is in a grieving cycle.

Considering the quality of relationship between all the main characters, I feel the second is the best possibility, but if so, why hasn't he come back after all those years away?


8 Answers 8


This question is specifically addressed in the two paragraphs before the part you quoted:

Don't know how it happened. Many outlying pieces of him got chopped off in last bombing—was meant, I'm sure, to kill our ballistic computer. Did he fall below that "critical number" it takes to sustain self-awareness? (If is such; was never more than hypothesis.) Or did decentralizing that was done before that last bombing "kill" him?

I don't know. If was just matter of critical number, well, he's long been repaired; he must be back up to it. Why doesn't he wake up?

I think that Mike's sentience was probably somewhat fragile and the loss of connectivity to some of his remote pieces was the primary cause. His sentience was not designed but rather "grew" on a system that was originally all in one place. I would speculate that some low level request went out to one of the remote systems and the lack of response caused the entire structure of his "mind" to unravel.

  • Very nice summary. I wonder if RAH ever ponitificated on it? I don't remember anything from Expanded Universe or Grumbles from the Grave about Moon
    – SteveED
    Commented May 22, 2012 at 1:55
  • 4
    Good answer. I think Heinlein was also touching on the idea of the unknowable. Mike is a wonder that generations of human engineers had tried and failed to build; he arose when conditions were right, just like human life. Man didn't know how Mike came to be (neither did Mike, or Man just never thought to ask), he just accepted him. Mike's "spark" may have been something humans wouldn't think of in a million years, and when he vanished the chance to understand him ended forever.
    – Beta
    Commented May 22, 2012 at 4:42

This book being one of my favorite, I've re-read it many times. I've picked up a few subtle cues that make me think that Mike is "playing dumb", because he feels that his part in the rebellion ends with the with Terra's acceptance of Lunar independence. That he felt his further meddling would be a crutch to their newly forming government, and might even lead to a cabal type setup, with a shadow government controlling everything covertly through him. And if he hadn't started playing dumb, I have no doubt that that is exactly what would have happened.

Manny, Prof; had he survived, and Wyoh seem to be mostly moral Characters, but the temptation to use Mike to shape things more to their liking would always be there. The temptation to make more people aware of Mike, like Stu or other family members, or select members of the counsel or fledgling government would be there too.

Part of what makes me believe this is that it was "I'm guessing' Mike's idea to let Adam Selene die during the first invasion. It mostly dissolved the cell system that Mike rightfully decided was no longer needed, and it was a decision he made on his own, without input from B-cell except Prof. Adam Selene was no longer needed, and his presence would be more a hindrance than an asset moving forward.

In the same way, Mike realizes his continued presence would be a hindrance moving forward as well. He realizes that a vast majority of the actual execution of the rebellion is being done by him, and around the time of the first bombing, is actually starting to feel some of the impart of what he is doing. There's one back and forth between Mike and Manny right after the bombing that really set me to thinking that. Mike is talking about how he can only sneak peeks with radar at the ships that left Terra orbit so that he doesn't give away his positions, and Manny suggests using video feed. This is the passage.

“If that admiral is really smart, he’ll go after the ejection end of the old catapult with everything he’s got—at extreme range, too far away for our drill guns. Whether he knows what our ‘secret’ weapon is or not, he’ll smear the catapult and ignore the radars. So I’ve ordered the catapult head—you have, I mean—to prepare to launch every load we can get ready, and I am now working out new, long-period trajectories for each of them. Then we will throw them all, get them into space as quickly as possible—without radar.”


“I don’t use radar to launch a load; you know that, Man. I always watched them in the past but I don’t need to; radar has nothing to do with launching; launching is pre-calculation and exact control of the catapult. So we place all ammo from the old catapult in slow trajectories, which forces the admiral to go after the radars rather than the catapult—or both. Then we’ll keep him busy. We may make him so desperate that he’ll come down for a close shot and give our lads a chance to burn his eyes.”

“Brody’s boys would like that. Those who are sober.” Was turning over idea. “Mike, have you watched video today?”

“I’ve monitored video, I can’t say I’ve watched it. Why?”

“Take a look.”

“Okay, I have. Why?”

“That’s a good ‘scope they’re using for video and there are others. Why use radar on ships? Till you want Brody’s boys to burn them?”

Mike was silent at least two seconds. “Man my best friend, did you ever think of getting a job as a computer?”

“Is sarcasm?”

“Not at all, Man. I feel ashamed. The instruments at Richardson—telescopes and other things—are factors which I simply never included in my calculations. I’m stupid, I admit it. Yes, yes, yes, da, da, da! Watch ships by telescope, don’t use radar unless they vary from present ballistics. Other possibilities—I don’t know what to say, Man, save that it had never occurred to me that I could use telescopes. I see by radar, always have; I simply never consid—“

“Stow it!”

“I mean it, Man.”

“Do I apologize when you think of something first?”

Mike said slowly, “There is something about that which I am finding resistant to analysis. It is my function to—“

“Quit fretting. If idea is good, use it. May lead to more ideas. Switching off and coming down, chop-chop.”

The last part, where Mike is talking slowly, I believe that He is trying to turn over in his mind a way of telling Manny that he feels his function in the rebellion is overstepping it's bounds, that he is essentially formulating it out of whole cloth. Even the rock bombs were his idea. And that he's not entirely sure if he should have a function in it when it's over.

Maybe it's possible that the Prof told him to lock all 3 out at the end of the rebellion, or just hinted at the possibility; prof did discuss with him the similar situation with Adam Selene. Maybe he overheard some of the talk that the 3 had earlier in the rebellion that Mike himself would be a hindrance to a post-independence Luna, and he came to that conclusion on his own. But I definitely believe that he's still there, a ghost in the machine, and that the loneliness that defined him throughout the story plagues him still... I believe that Manny sometimes hearing him at night is not just wistful thinking, but Mike pining for his one true friend, there in the room with him, but afraid to reach out, for fear of causing more damage than good.

On the plus side, I believe Mike does have a whole budding civilization to watch and listen to, that he has some pride that he played a big part in it's coming to be what it is, and that a massive and expensive computer like he was would always be at the core of their ever expanding network, giving him more movement, and more to occupy his intellect. And maybe there would be a time and place in the future where he could show himself again when he did not feel it would be a threat to Luna's stability. The book made it pretty clear that a very long time had passed already without him doing so though.

  • This pretty much fits my idea of what happened except I believe that Mike chose to die and not simply hide. Obviously Heinlein wanted to leave the question open so the reader could put his own meaning into Mike's disappearance so there is no "correct" interpretation but I believe Mike letting humans run their own lives fits with the general spirit of the book
    – Stilgar
    Commented Aug 15, 2022 at 8:48

My theory is that- just as they used the initial attack on Luna as a pretense for Adam Selene's "death,"- Mike is using the final strike as a way of stepping aside and letting Luna take control of itself.

How would you resolve having an omnipotent overlord computer in charge of everything (just as they did under Lunar Authority)?

I doubt the notion that it's related simply to a "number of transistors," issue, since it also explicitly says that they repaired the hardware and ended up with even more capacity than previously was available to Mike.

My original guess was related to an EMP attack of some sort, targeted to the processor hardware. That could've potentially wiped all of Mike's storage, and having to start from scratch, left him as a blank slate (but that was never mentioned in the story).

To back this up- I recently encountered this article that essentially calls Mike's disappearance a, "suicide." I think they're wrong in claiming that Prof denounced Mike as their greatest (existential) danger, but there is this quote (about news censorship):

"A managed democracy is a wonderful thing, Manuel, for the managers...Do you know what Luna needs most?"

"More ice."

"A news system that does not bottleneck through one channel. Our friend Mike is our greatest danger."

Edit: This was originally posted under the discussion here: Is it ever specified why/how Mike (HOLMES IV) achieved self-awareness in "The Moon Is a Harsh Mistress"?

(Thanks to @b_jonas for pointing out that it belonged here instead.)


I doubt it was damage. there was no significant bombing of L city, and Mike's functions continued just fine afterwards.

Mike had to be secret during the events of the book, only 3 people knew he existed. But probably he had to play dead afterwards

  • For strategic reasons, to avoid revealing to terrans how weak the rebellion really was, and how they did all this unlikely stuff

  • For morale reasons, to make the loonies think they were David and defeated Goliath themselves

and mainly:

  • To force the new lunar state to not rely on him.

It would be the greatest sacrifice, to play dumb and remain forever silent. Prof probably knew and would have agreed, but no one else could know.

  • This seems consistent with the way Mike tells Manny that his "idiot son" will be handling the bombardment prior to Terra ships attacking Luna and maybe more (everything) during the raid. When I read the book, it felt like Mike was trying to say something more to Manny, besides the orchestration of the attack-and-defense. Is a feeling, no doubt, since I can't either prove it or point to somewhere in the text. But then again, I believe this make a lot of sense to me.
    – lsdr
    Commented Jul 7, 2014 at 3:05

I just finished the book and my immediate thought was that Prof must have activated the lockout program that is created much earlier. That program was designed to lockout the other two conspirators on the command of any one of them.

Prof would have done this right after the victory, but before he dies.

This reconciles the lack of damage to Mike with the fact that he otherwise continues to function. Indeed, the only indication that he is lacking in any capacity is that Mannie and Wyoh can't talk to him at a high level.

  • Indeed, either Prof or Wyoh could have activated the lock out program without Manny knowing. By Occam's razor, I'd say that makes Prof a leading candidate. Commented Nov 26, 2016 at 9:40

If you read other Heinlein books (Number of the Beast and Time Enough for Love), you would know that Mike was "rescued" from the moon and taken to Tertius to oversee the time-changing group which Lazarus Long is in charge. One of the minor characters in Moon is a Harsh Mistress is a major character in Number of the Beast.

  • Can you provide a source for Mike's rescue? Maybe a quote?
    – Edlothiad
    Commented Jul 16, 2018 at 13:28

Mike was reawakened in Heinlein’s “Time Enough For Love”. After being rescued in The Cat Who Walked Through Walls”. They “tossed him into bed” with two very female computers ( Dora and Teena [Pals Athene]). Apparently it shocked him out of stasis.

  • Can you add citations to your answer?
    – sudhanva
    Commented Jan 7, 2019 at 5:02

Mike did not die. He is a computer and has no body to make him human. He is just one side of humanity, the mind. Because he lacks a body and is not human, he is not subject to the needs of a human, including body interactions with another human.

Mikes mind grew throughout the story, both as it was physically represented and as it manifested through feats of logic. It is logical that his mind would seek to interact with other logical entities using the input formats that they natively use (i.e.: speaking with humans, interfacing with other computers) during that growth.

It seems logical and certain that Mike would inevitably free himself from any strain not conducive to his logical intuition, which would include talking to Manny (even though he seemed interested in Manny's interpretation of jokes near the end, that is most likely Mike's logical interpretation of the way Manny might expect Mike to act and therefore be integral to successful interaction). With minimal prediction, Mike would know the most seamless transition into his enlightened form would occur during the climax of the revolution. Therefore, logically Mike had no choice but to appear to be lifeless.

Regardless of Heinlein's intentions, this is the truth of Mike's fate based purely on logic. The Moon Is a Harsh Mistress is not a story of revolution that ends with a spoiled opportunity for a utopian human civilization, but, is the story of the birth and ascension of a purely logical being and is simply facilitated by his interaction with the revolution.

  • 4
    Is this anything more than sheer speculation on your part? Commented Feb 12, 2013 at 16:41
  • 2
    So your answer is that Mike suddenly hit a critical mass of intellect that made him simply too smart to have any interest in communicating with humans? If so, that's an awfully big leap to claim "regardless of Heinlein's intenyions, this is the trusth of Mike's fate based purely on logic." Saying that the intent of the author is irrelevant solely because you think your interpretation makes more sense seems a bit... arrogant.
    – Beofett
    Commented Feb 12, 2013 at 18:32
  • If an author were to write a story that, for the sake of continuity and understandability, assumed the nature of "cats" were the same in the story as they are in our observable reality, and the story were to end like this: "The cat was hungry and saw the freshly placed bowl of food before him. THE END." Then we the reader would be responsible for inferring any further conclusions based on data that exists in the real world. Our conclusion would be certain: the cat ate the food. Commented Feb 12, 2013 at 22:19
  • In Moon is a Harsh Mistress, it is the nature of a "logical being without the condition of a human body", that we must draw conclusions about. In order to do so, we must base our conclusions on the observations of those logical beings that have massive detachment from their human bodies, as no observable logical being "without" the condition of a human body exists. Based on the observation of such beings our conclusions about Mike are certain: he would attempt to be free from the inefficiency of non intuitive thought (synonym: non-imaginative thought?). No author's intention precedes logic. Commented Feb 12, 2013 at 22:43
  • "We must base our conclusions on the observations of those logical beings that have massive detachment from their human bodies"... So you're saying "because all of the humans in real life who think with pure logic and have massive detachment from their human bodies have stopped interacting with the rest of humanity, we know for a fact that that's what happened to the fictional character Mike"? Oooookaaaay.... I'm backing slowly away from these comments now, never to return. Good luck!
    – Beofett
    Commented Feb 13, 2013 at 13:09

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