(A shorter gloss of Fun Theory is "31 Laws of Fun", which summarizes the advice of Fun Theory to would-be Eutopian authors and futurists.)

Fun Theory is the field of knowledge that deals in questions such as "How much fun is there in the universe?", "Will we ever run out of fun?", "Are we having fun yet?" and "Could we be having more fun?"

Many critics (including George Orwell) have commented on the inability of authors to imagine Utopias where anyone would actually want to live. If no one can imagine a Future where anyone would want to live, that may drain off motivation to work on the project. The prospect of endless boredom is routinely fielded by conservatives as a knockdown argument against research on lifespan extension, against cryonics, against all transhumanism, and occasionally against the entire Enlightenment ideal of a better future.

Fun Theory is also the fully general reply to religious theodicy (attempts to justify why God permits evil). Our present world has flaws even from the standpoint of such eudaimonic considerations as freedom, personal responsibility, and self-reliance. Fun Theory tries to describe the dimensions along which a benevolently designed world can and should be optimized, and our present world is clearly not the result of such optimization. Fun Theory also highlights the flaws of any particular religion's perfect afterlife - you wouldn't want to go to their Heaven.

Finally, going into the details of Fun Theory helps you see that eudaimonia is complicated - that there are many properties which contribute to a life worth living. Which helps you appreciate just how worthless a galaxy would end up looking (with very high probability) if the galaxy was optimized by something with a utility function rolled up at random. This is part of the Complexity of Value Thesis and supplies motivation to create AIs with precisely chosen goal systems (Friendly AI).

Fun Theory is built on top of the naturalistic metaethics summarized in Joy in the Merely Good; as such, its arguments ground in "On reflection, don't you think this is what you would actually want for yourself and others?"

Posts in the Fun Theory sequence (reorganized by topic, not necessarily in the original chronological order):