When I read the title of this post, and then the line about "a Just-So story, true enough for our purposes" I almost jumped right to to the bottom to make an indignant comment. I'm glad I didn't, though, because this sounds like something really worthwhile.

One of the things I picked up from this blog was the idea that the various bits of mental machinery used by things like religion and politics could also be used to support ideas that had been thought about first and believed second, and I think this is a great example of that.

With that said, though, those bits of machinery are dangerous. Even if (for example) we've seriously calculated existential risk to be high, the more emotionally invested you are in the idea, the less weight you're likely to give to any evidence that might show it to be lower than we previously thought.

So long as we don't go overboard, I think rationalist holidays are a fantastic idea, but be careful.