Jump to ratings and reviews
Rate this book

Three Worlds Collide

Rate this book
Three Worlds Collide is a story I wrote to illustrate some points on naturalistic metaethics and diverse other issues of rational conduct. It grew, as such things do, into a small novella. On publication, it proved widely popular and widely criticized. Be warned that the story, as it wrote itself, ended up containing some profanity and PG-13 content.

56 pages, ebook

First published January 30, 2009

Loading interface...
Loading interface...

About the author

Eliezer Yudkowsky

46 books1,781 followers
From Wikipedia:

Eliezer Shlomo Yudkowsky is an American artificial intelligence researcher concerned with the singularity and an advocate of friendly artificial intelligence, living in Redwood City, California.

Yudkowsky did not attend high school and is an autodidact with no formal education in artificial intelligence. He co-founded the nonprofit Singularity Institute for Artificial Intelligence (SIAI) in 2000 and continues to be employed as a full-time Research Fellow there.

Yudkowsky's research focuses on Artificial Intelligence theory for self-understanding, self-modification, and recursive self-improvement (seed AI); and also on artificial-intelligence architectures and decision theories for stably benevolent motivational structures (Friendly AI, and Coherent Extrapolated Volition in particular). Apart from his research work, Yudkowsky has written explanations of various philosophical topics in non-academic language, particularly on rationality, such as "An Intuitive Explanation of Bayes' Theorem".

Yudkowsky was, along with Robin Hanson, one of the principal contributors to the blog Overcoming Bias sponsored by the Future of Humanity Institute of Oxford University. In early 2009, he helped to found Less Wrong, a "community blog devoted to refining the art of human rationality". The Sequences on Less Wrong, comprising over two years of blog posts on epistemology, Artificial Intelligence, and metaethics, form the single largest bulk of Yudkowsky's writing.

Ratings & Reviews

What do you think?
Rate this book

Friends & Following

Create a free account to discover what your friends think of this book!

Community Reviews

5 stars
661 (43%)
4 stars
561 (36%)
3 stars
222 (14%)
2 stars
58 (3%)
1 star
22 (1%)
Displaying 1 - 30 of 107 reviews
Profile Image for Lee.
5 reviews
April 16, 2021
This story takes place in a utopian future, where “humanity got its shit together”.
Let’s address the elephant in the room, the author wants us to know that rape has been legalized in this bright future.

Is it important for the story, does it advance the plot? No. Why is it added in the first place? Apparently it’s to illustrate how quirky and weird the future is, and that an old character that remembers present time (where rape is bad) can’t make decisions in that bright future, because well he wouldn’t have legalized rape, and yet it was somehow the correct thing to do.

A quote (it has nothing whatsoever to do with the plot so it’s not a spoiler)
>”I expect everyone was glad to have that law taken off the books. I can't imagine how boring your sex lives must have been up until then - flirting with a woman, teasing her, leading her on, knowing the whole time that you were perfectly safe because she couldn't take matters into her own hands if you went a little too far -"

Commenters on the website where the story’s published feel very clever when they point out how it’s a-c-t-ually a subversion, and the character obviously means that the woman is the one who's supposed to rape the man in his scenario, because, you see, in this future women are as strong as men!
News flash, the world doesn’t consist of straight dudes and women they want to have sex with, this “subverts” nothing: for instance, men presently rape other men as well, it doesn’t cleanly come down to women being physically weaker.

“Well what about BDSM, the author has a note at the end of the chapter saying that:
“In real life, continuing to attempt to have sex with someone after they say 'no' and before they say 'yes', is defined as rape”
and “Some people have worked out a safeword system in which they explicitly and verbally agree, that 'no' doesn't mean stop but e.g. 'red' or 'safeword' does mean stop. I agree with and support this”
clearly he just means they legalized BDSM!”

BDSM, and what the author described in the note, isn’t rape and is perfectly legal, this “author’s note” is infuriating.

“Well then it means the consequences for the victim are now so small because of the healthcare/psychiatric help/etc etc”

Why does it have to be rape then? Let’s have a bright weird future where non-consensual limb removal is legalized. Chopping somebody’s arm off is perfectly legal now.

“But that won’t work in a story at all, wanting to chop somebody’s arm off isn't relatable!”

As opposed to what? The readers are supposed to find this relatable, don’t they. So when they don’t, it falls catastrophically flat.
(if you want to argue that it’s about knowing that “other messed up people” would want it, instead of it being relatable to the reader themselves, imagine if instead of rape it was pedophilia; a whole paragraph describing how boring it was when pedophilia was illegal, and how you would lead a child on, etc. Changes things, doesn’t it. Don’t worry, children are strong in this future, and there’s great healthcare!)
Profile Image for Hussain Elius.
127 reviews106 followers
July 10, 2012
I wish Eliezer Yudkowsky was a full time writer. So many good ideas!

This novella was about humans encountering the alien race of Babyeaters - who are civilized but eat their babies, and the humans, as soon as they learn of this, are morally shocked about the custom that is taken to be natural. Most of them want to wage war to save the babies (so cliche) and relieve them of their pain! But then, another alien race arrives, the Maximum Fun-Fun Ultra Super Happy People. One that thinks even having pain is morally repulsive, and want to rid humans of physical and mental pain, and make them... less human.

Of course there is no right or wrong answer. And that's what makes a philosophical discussion about it so great. If as humans we want take enforce our morality on another race, what's stopping another race from doing so, too?
Profile Image for Alan.
151 reviews2 followers
April 20, 2018
CW: rape mention, murder mention, weird anime shit

OKAY I read that whole HP Rationality book aaaages ago, back when it was still being serialized, and at the time it seemed pretty good! (Now that I'm not an impressionable teen, it... really doesn't.) But for some sadomasochistic reason, I decided to read one of his other, SHORTER stories. IT'S TERRIBLE.

All quotes are in spoiler brackets so that you can easily avoid them :)


the free real estate meme but bad writing
Profile Image for Петър Стойков.
Author 2 books322 followers
February 13, 2021
Хората сме много "морални" същества - имаме неистова нужда да си изграждаме морални правила, да ги възприемаме за правилни и да ги защитаваме. Това е част от нашата природа и не можем да го избегнем, колкото и да се стараем.

Независимо дали ги обличаме в религия, идеология или "светоглед", всички си мислим, че начинът, по който мислим и възприемаме света и действията на другите хора е единственият правилен. Дори да се имаме за много "толерантни", много лесно се намират въпроси, пред които моралното ни чувство почва да беснее и ни превръща в кръвожадни диваци, които крещят в лицето на "лошия" колко е лош и искат да му разбият главата с камък.

И наистина, моралът е толкова дълбоко и коренно заложен в мозъците ни, че може да накара и най-цивилизования човек да се превърне в демон, да го накара не само да върши неизброими злини, ами и най-лошото: да го накара да си мисли, че е прав, когато ги върши, че той е добрият, а тия, които страдат от ръката му са лошите.

Това състояние на нещата може да се види всеки ден в обществото ни, в политиката, в историята. Даже днес съвсем не са малко хората, даже в цивилизования западен свят, които крещят по улиците, събират се на тълпи да палят и чупят и искат да разбиват главите на "другите" - със съвсем благородни мотиви, естествено.

Но какво ще стане, ако доведем моралните си чувства до абсурдни висоти, в абсурдна ситуация? Колко хора трябва да убием, за да възтържествува доброто?
Profile Image for Scott.
23 reviews3 followers
March 22, 2019
An interesting science fiction long short story (100 pages). It reminded me of I, Robot, except instead of quaint 1950s charm ("positronic brains") it has awkward references to internet culture ("Any suggestions get reddited up from the rest of the crew?"). I made an EPUB version for ereader users.
Profile Image for Shayan Kh.
279 reviews24 followers
September 26, 2015
Yudkowsky is officially one of my favorite thinkers. Too bad he doesn't write more often. I liked the way he shaped hpmor, although I didn't like the whole story. But this time around, he presented a very disturbing version of prisoner's dilemma, in a sci-fi about different kinds of sentient beings, and how their morals might be radically different from ours. It is very thought provoking and I really enjoyed this piece of work.
I hope He writes more stories. I'm definitely gonna read his work.
Profile Image for Caleb M..
575 reviews29 followers
January 20, 2022
What an incredibly unique little book we have here. I think this book was written specifically because the author had some crazy ideas and wanted to write them down into a form that would be coherent and make some kind of sense. It's thought provoking and philosophical and also not 100% my jam.

I love philosophy and thinking about things that shoulda, coulda, woulda or what have you. Which is why this book garnered a 3 star. As a book and as a story though this wasn't to great. It's to bad it couldn't be more fleshed out though and turned into a full length novel because if it did then I think that it could be on the level of Xenocide for me. But, alas, it was short and not fully stretched out into the goodness I think it could have been. Don't get me wrong, I like shorter stories, but this one just felt like it didn't have enough time to nail down everything it wanted to hammer. If that makes any sense.

Interesting little book for sure. And a free read is always nice.
Profile Image for Karl.
408 reviews66 followers
February 16, 2018
Maybe the best short story I ever read. If you do not get HPMOR, you should anyway try this.

This is like Star Trek but orders of magnitude better. These 100? pages, contain the intellectual value of 2000 pages of traditional sci-fi, and without the nonsense.

If Yudkowsky is not canon in 2100, then canon is mostly random. He is Borges and Bertrand Russel in one.
Profile Image for Danielius Goriunovas.
Author 1 book260 followers
May 31, 2023
Skaityti - buvo smagu. Bet neįsiminė. Istorija išskirtinė, rašymas geras, bet tiesiog, hm, gal trūko moralo? Klausimo? Drąsaus išskirtinumo?

Bet džiaugiuosi skaitęs.
Profile Image for Quinn Dougherty.
56 reviews9 followers
November 17, 2019
Highly recommended. Haunting, I continue to think about it almost every day even months after I read it. The most sober reasoning about alienness that you're likely to find. One of its conclusions/provocations, that if you look at the distribution of possible space-faring civilizations, it's probable that if they're legible/recognizable at all then they're morally monstrous. At the same time of course a future, space-faring humanity may also be monstrous. Do explore this idea by reading the whole story (or, as I did, the audiobook from eneasz brodski at hpmorpodcast.com).

I especially recommend to fans of Butler's Xenogenesis--- similar, sometimes identical themes explored with a very different choice of granularity/lens.

Warning-- some aspects of the story aren't recognizable or intuitive if you're not a card-carrying cultmember of transhumanism/enlightenment, but for the most part it's a gentle introduction.
396 reviews30 followers
September 25, 2018
The writing felt a bit cringey at times, but I’m glad I got past that to the actual concept, which was really interesting.
Profile Image for Jesper Lindholm.
29 reviews
July 12, 2024
Masterfully written first chapters. 5/5.Then the writer advances the story beyond his capabilities as a writer and original thinker. This decreases the credibility of the fiction.

It is still an interesting story. Quite hard to follow all dialogue in the later chapters.

There are some dilemmas with obvious solutions left untested, which raises questions of false dilemmas, as far as rationality goes. (This is a rationalist fiction). Also some disproved scientific details, but they do not affect the plot very much.

On the whole, a thought provoking sci-fi.
Profile Image for Zach Toad.
31 reviews
January 25, 2015
Insanely thought-provoking, but didn't quite get all the references to game theory other than talk about the prisoner's dilemma. I wish I had a college level game theory course under my belt before reading this. The play with ideas in metaethics was very well-done, however. Relevant, too, to all our political conflict over whether to intervene or not in foreign affairs.
Not sure that it brought me any closer to answers!
Profile Image for Suraj Amlani.
32 reviews
August 13, 2023
Thought provoking short novella about a spaceship meeting 2 alien species, and the massive culture clash they have. Clever integration of game theory along with some imaginative thinking about what other sentient beings could be like with their own values (babyeaters / super happy fun fun). Deducted a star for some odd statements about rape randomly thrown in the middle and another for the confusing 2 alternative endings. Story could have been filled out a bit more too.
Profile Image for Kateřina Valová.
206 reviews6 followers
October 14, 2020
Opravdu zajímavý a neotřelý pohled na střet naší civilizace s "mimozemšťany". A nebo taky (sociálně) antropologické zamyšlení nad přijímáním jinakosti druhých. Nebo třeba ukázka toho, kolik vrstev se dá vměstnat do jednoho krátkého příběhu.
Profile Image for Tarmo Pungas.
166 reviews6 followers
August 20, 2021
Whether you've wondered how we would perceive aliens or they us, this offers a unique perspective. When I say unique, I mean "eating babies" unique. It also made me think of how much suffering still exists (after all this progress) on Earth.
Profile Image for Sam .
57 reviews19 followers
April 21, 2021
I've read this before, but I re-read it now for a paper; I think I picked up on more of it this time. Weird, entertaining, and makes you think. Not that I agree with every point the author makes, but I still appreciate it
114 reviews8 followers
September 2, 2019
Reminded me of The Three Body Problem, Dark Forest, and Harry Potter and Methods of Rationality (probably because of audiobook narration by same people). It's a short novella, I wish there was more.
171 reviews6 followers
May 12, 2019
This does a very good job of presenting an intuitively graspable version of the prisoner's dilemma vis a vis a paperclip maximizer (in the general sense, a foreign intelligence whose goal function shares no resemblance to our own). Recommended follow-up reading: Superintelligence and Friendship is Optimal.

Setting presentation, design and originality (how cool is the setting?): 5
Setting verisimillitude and detail (how much sense does the setting make?): 5
Plot design, presentation and originality (How well-crafted was the plot, in the dramaturgic sense?): 5
Plot and character verisimillitude (How much sense did the plot and motivations make? Did events follow from motivations?): 5
Characterization and character development: 5
Character sympatheticness: 4
Prose: 5
Page turner factor: 5
Mind blown factor: 5

Final (weighted) score: 4.9

Available at: https://www.lesswrong.com/posts/HawFh...
Profile Image for Eric Herboso.
68 reviews31 followers
December 15, 2021
This short story describes a spaceship of humans in the future who make first contact with not one, but two intelligent alien races. The result involves spirited debate as each of the three realize they all have very different views on which moral facts are true.

If you have a group of friends interested in metaethics, I strongly recommend you try printing out hard copies of this short story in sections, and read the story together in person. Each successive section will give you a lot to talk about, and there are few enough sections of short lengths that it will only take around 2.5 hours to read through every section with plenty of conversation between each.

Those not as interested in metaethics will still get something out of the story, though they might not rate it as highly as I have.
Profile Image for Jeremy.
41 reviews2 followers
January 1, 2016
I find the characters impossible to relate to. You might say that's beside the point for this particular story, but I think it exactly is the point for a case of first contact with an alien (in all senses) culture. Here, I felt that all the species were alien.

The story describes certain alien behaviors that produce visceral emotional reactions in the characters (and for good reason, probably). And yet I had no emotional reaction myself, which I don't think was the reader's fault.

The author can be somewhat heavy-handed at the best of times, and this novella is certainly no exception.

On the other hand, the novella is very short, and the thought experiment is worthwhile. So you could make a friend read it then summarize it to you. The subsequent discussion between the two of you would probably be more interesting than the novella itself.
Profile Image for Dessislava Ivanova.
320 reviews15 followers
October 22, 2021
OK, that mini book (or novella) was a real emotional rollercoaster for me - I felt hopeful and also super sad. It was a scary and a happy reading. And my moral compass was spinning like crazy because I was so confused! We think we know what's good and bad and want to enforce our "truth" to everyone but what if some alien race is exactly like that but also with a totally different moral? The reasoning in this story is so good - the writer is a thinker on a whole new level and was tinkering with my brain all the time. So many questions and no wrong (or right) answers. Or maybe some wrong answers but who can say that really? I liked the absurdity and the possibility of it all. And the alternative endings because the entire story is made of alternatives.
Profile Image for Ana.
509 reviews8 followers
June 28, 2015
Interesting dilemma set in a future where space travel is common and people have colonized multiple planets. I'm not sure I understand or agree with the assumption that all must create a homogenous society. It's meant to illustrate the prisoner's dilemma but really gives a false choice that I would hope in future societies would not be considered a choice at all. Why does one group of aliens feel the need to convince the others of their moral correctness? This feels more like a piece on religion than morals or the prisoner's dilemma.

Interesting premise, but a bit too preachy and one-sided to me.
This entire review has been hidden because of spoilers.
24 reviews2 followers
January 26, 2019
Short, gripping and stunningly intuition-wracking. The story of three different species with three different evolutionary histories meeting reveals much about our own ethical intuitions as a species as of now (~early 21st century). Especially tasty is the way that the story unveils some (possibly hidden) preferences in the reader (humans should win/prevail etc.) and this brings the themes of the story into the real world for further discussion.

This short story is brief enough that it can be read in an evening and will be enjoyed by anyone interested in science-fiction, rationality, ethics, and game theory.
Profile Image for Simona.
209 reviews36 followers
October 2, 2016
I loved it. If playing the classic prisoner's dilemma, you cooperate with a single individual. Almost always. You defect only in fear. But what if you really-really want to defect and you are playing against aliens for whom you are morally disguising, and you feel the same about them.
Amazing story, well written, strange, thought-provoking. Nice to accompany it with the original reader comments on Less Wrong.
I recommend it
Profile Image for Fulmenius.
78 reviews2 followers
August 21, 2021
A perfect example of Yudkowsky's fiction, containing at the same time humor, smart characters, non-trivial moral dilemmas and mind-blowing plot twists
13 reviews
September 18, 2023
I liked HPMOR. I don't know how it'd hold up on a first read now, but HPMOR is at least entertaining and interesting, and has interesting takes on the characters, no matter how obvious it is that Yudkowsky has never even looked at the books.

This one... Well, to some degree, up to a point, there were interesting points about the ethics of other alien species. I think they were all being unreasonable in not just calmly expressing what they don't like and then letting each other be, but that could easily be part of the story.

Then we get to the humans apparently being super enlightened and the absolute state of human morality in this universe. The humans are described as enlightened but they jokingly talk about stuff that is FAR beyond "Pg-13". I mean that paragraph alone where it's described should be seen as 18+. There's a ship 4chan and that's seen as normal, and not like a major sign that humanity has descended into bigotry. Yudkowsky should have just joined r/incels and been done with it. He's made it basically impossible to consider reading anything else from him because he doesn't seem to be being ironic about any of the random mentions of internet culture.

I understand the point about it being more interesting if the humans are okay with something morally repulsive, and I do agree... but there were a lot of options here, including things people actually DO - maybe people are still using capitalism, so still value the richs' big pockets over the poors' lives. Maybe there's still privatised healthcare, so we still value the richs' big pockets over the poors' lives. Maybe sweatshops are the norm, because we still value the richs' big pockets over the poors' lives. Maybe most people are homeless, and landlords have a monopoly on the worlds' housing, causing people to have to leave the planet for space, because we still value the richs' big pockets over the poors' lives - are we maybe spotting a pattern here of something that would have been FAR more interesting as the messed up morally repulsive thing humans can be doing??? The interesting but also very low hanging fruit analogy that was right there and far more interesting because it'd actually be relevant to society? I mean, hell, it doesn't need to be something that obviously political. Pick anything society ACTUALLY does that's morally disgusting, exaggerate it slightly, and make that the bad thing humans do, and VOILA, the story has an actual point it's getting at, the story is much more interesting, the analysis and themes are more interesting, AND the author doesn't have to out himself as an incel. It's really that easy to make the story that much better.

I don't think I'll be able to read anything else by Yudkowsky after this. There's really no coming back from an author outing themself out as an incel. You just won't ever be able to enjoy their work again.

A major disappointment after HPMOR.
Profile Image for Rebecca.
1,293 reviews3 followers
August 30, 2023
There are some great ideas in this book, mostly on the topic of ethics, meta ethics, morality, and what would happen in a first contact scenario. A strange future humanity meets two alien species, each with a bizarre form of morality to humankind. The Babyeaters do what their name implies: eat their young, and their word for “being good” is the same as the word for “eating babies”. The Super Happy People are completely hedonistic, have eliminated pain, and transfer their thoughts through sexual intercourse. The best parts of this story are descriptions of these aliens and how their different views of ethics clash.

Humans are weird in this one, and sometimes they also feel like aliens. They see their future as the best possible future, but I’m not inclined to agree. They are weirdly hierarchical and occupation-oriented, addressing the people in the most senior positions with titles of nobility. They are quite capitalist, running spaceships using the stock market. The differences serve the story well, making the humans more interesting, except they have legalized rape. That’s the worst part of the story for me. Legalizing rape, even if social attitudes towards rape and how raping is done have changed a lot in the future, would cause many social problems and make other problems much more common. It’s also disgusting.

The plot is not that great, but it is passable. It mostly comes out of logic and what decisions characters would rationally make. There are two endings, and each one services the needs of this story in different ways. The normal ending is what would probably happen, and the true ending was written by readers who wanted a happy ending. I can’t decide which one I would like best.

I didn’t like HPMOR, so I guess the author is better at writing original fiction than fanfiction. That, or this story is about philosophies different from his own. I loved this story a lot, mostly the first few chapters, and except for the rape thing. If the attitude towards legalizing “nonconsensual sex” didn’t read so wrong to me, I would have given this story the full five stars.
Displaying 1 - 30 of 107 reviews

Can't find what you're looking for?

Get help and learn more about the design.