"Even if this conclusion is wrong, what do you think the proper method is to deal with the irrational nature of humans? Set up some sort of inner cabal of "great minds" to run the world (ignoring the fact they're just as human, therefore just as irrational, as anyone else)? Try to find some inhuman ("angelic") agent to run the world, and hope their goals remain humanly comprehensible? Or just give up and go back to the caves?"
Say me and you don't have time to figure out enough while we are alive, we can agree there is a reality out there that we need to know to survive yes? Our main problem as human beings as there is no consensus as to what 'reality' is, or who's judgement is functioning properly (aka people feel left out, hurt feelings, 'fairness',etc). Plato explored this problem, since it is in no way new.
So let us up the stakes, let's say there's a nuclear bomb and we know there is only a tiny number of educated people that can diffuse it. (This is why we have education after all). Now probably even the most (insert political label here) takes physics seriously provided they as an animal have a deep respect for science and evidence over their feelings. AKA survival and truth comes before politics, and politics has to change if it gets in the way of survival in this case. So when push comes to shove we want someone who is scientifically informed about the laws of nature, we don't want joe sixpack (aka chances of disarming the bomb go way up and that is a good thing).
Survival being something everyone can agree on and usually when someone tries to be a dumbass we get rid of him from our society/tribe, yes?
So we'd develop a system of reasoning related to long term survival, now in the ancient world... it would make sense anyone who disagree'd with it we'd get rid of (either by prison or killing depending on the situation). Since if you don't survive, there isn't really any room for debate now is there?
Now in our time, the "good" half of the elites in the corporate world and upper classes believe in the dictatorship of the best and brightest (aka the smart over the stupid). The downside is that there is not enough of them and there is no guarantee that they are mature (just look at the bailouts).
Basically it would come down to us developing techniques to ferret out our own lies and illusions, there must be a method that we just haven't discovered/come up with yet (consider you reading this right now, you know that you 100% exist in order to read this text, so we begin with the brute fact that we exist, and try to figure out the relationships that are connected to this one brute fact of existence which we can base our knowledge upon). Since even if our brain is flawed, there still must be stuff that works 100% or else we couldn't have survived. So the answer MUST be in our biology. Just what is the ruler the mind is using to measure the universe, at the foundation of mind there must be an absolute idea/concept from which to build a theory of truth regarding long term survival. (aka the door is open or closed, if we couldn't know, we couldn't decide and hence hurt ourselves).
Now the utlimate rule by which people stay or go is: People who have respect for truth, survival and the laws of nature and people who don't. Our problem comes with giving respect to people who just don't value these things. These people need to be mocked/shamed/whatever'd. We'd have to find some way to deal with them.
That's what this comes down to in the end, those of us who are adults and the rest of mankind who are teenagers/childish. Since a respect for what is true is respect for your own survival (aka the highest value, since it is the foundation of everything else we value).