Book Review: Methods of Rationality

It’s high time I did a real review of my favorite book in the universe. I read it for the first time at the age of 13, and it triggered an utter obsession with cognitive science, rationality, and artificial intelligence that has not disappeared to this day. (It has, however, become more mature: I no longer write shitty romantic poetry about cognitive science.)

I will attempt to describe this masterpiece of literature; more than once since I will absolutely fail several times.

Harry Potter and the Methods of Rationality is a 122-chapter parallel-universe Harry Potter fanfic in which Lily Evans married an Oxford professor, Michael Verres, and Harry was adopted and raised in a loving home filled to the brim with books. It is written by one Eliezer Yudkowsky, co-founder of the Machine Intelligence Research Institute, who writes frequently for the blog Less Wrong, which I’ve cited here before, and is best known for popularizing the idea of Friendly AI.

Harry Potter and the Methods of Rationality is a book about an eleven-year-old who knows both magic and calculus and wants to take over the world using Science so he can get more books.

Harry Potter and the Methods of Rationality is a book that successfully taught a 13-year-old girl—who wasn’t and still isn’t a genius—the underlying fundamentals of cognitive psychology, quantum physics, artificial intelligence, and Bayesian probability theory. If you read it, you will also learn these things, without ever realizing you have learned them. It will simply make sense, in a way that makes you wonder how you ever didn’t understand it.

While reading Harry Potter and the Methods of Rationality, you will frequently have absolutely no idea whether Harry is the villain or the hero. You will frequently have absolutely no idea whether Draco Malfoy is the villain or the hero, either. This goes for most of the characters, with the exception of Hermione and McGonagall. It does not exclude Voldemort.

This book will make you laugh, cry, learn, and question human existence. It will make you very aware of the sound of snapping fingers, and the shape of the night sky. It will show you the best and worst of humanity, and make both understandable. If you let it, it will teach you some of the most valuable life lessons you might ever learn.

Find the completed book at You can read it in however much time you like, but given the length, it takes a fast reader about three or four days to binge straight through, so you probably can’t read it any faster than that. In any case, when you do finish it, please leave a comment telling me what you thought! And of course, give the author some feedback and leave reviews on however many chapters you like.

As an end note, in case you might not have believed me, here is only one of the shitty romantic poems I wrote about rationality. Please be nice to the author, she was a little girl who fell in love with science, not a poet, and she was doing her best.

Be skeptical, not cynical;
be open, but not gullible.
Be curious, not clever;
no rationalization, ever.

Accept the truth for what it is;
and look for contradictions
in all arguments, yours included;
you’re more confused by fiction.

A word is just a label
before you know the referent;
a lie gets told a long time,
if someone’s to protect it.

Certain kinds of people
truth they wrongly construe,
but they’ll do it in the name of
who they think is watching you.

Humans tend to think
they could predict things in advance
but that’s some hindsight bias
when really there’s low chance.

Don’t explain all this all at once,
mind inferential distance,
plus the illusion of transparency,
and all peoples’ heuristics.

People don’t like weird ideas,
or saying they don’t know;
but even with our biases,
There’s a long way we shall go.