Our secret overlords won't let us build it; the Fermi paradox implies that our civilization will collapse before we have the capacity to build it; evolution hit on some necessary extraordinarily unlikely combination to give us intelligence and for P vs NP reasons we can't find it; no civilization smart enough to create strong AI is stupid enough to create strong AI; and creating strong AI is a terminal condition for our simulation.
Good points.
evolution hit on some necessary extraordinarily unlikely combination to give us intelligence and for P vs NP reasons we can't find it
For this one, you also need to explain why we can't reverse-engineer it from the human brain.
no civilization smart enough to create strong AI is stupid enough to create strong AI
This seems particularly unlikely in several ways; I'll skip the most obvious one, but also it seems unlikely that humans are "safe" in that they don't create a FOOMing AI but it wouldn't be possible even with much thought...
If Strong AI turns out to not be possible, what are our best expectations today as to why?
I'm thinking of trying myself at writing a sci-fi story, do you think exploring this idea has positive utility? I'm not sure myself: it looks like the idea that intelligence explosion is a possibility could use more public exposure, as it is.
I wanted to include a popular meme image macro here, but decided against it. I can't help it: every time I think "what if", I think of this guy.