What would a fully rational world do?
Of course this is completely impossible but it might be fun to think about.
I imagine that population control would be implemented such that the population stayed within some range so that there is always enough food without over fishing for example. I imagine that ”currency” would be based on something that had functional value and was limited or difficult to come by (think gold). I imagine some sort of energy use limits and I guess fossil fuels would not be allowed since those are limited. Once you start using fossil fuel you’ll just want more and more. So lets just say we dont start using fossil fuels at all. I imagine having less discretionary energy would prevent society from becoming more sophisticated than it was say a few hundred years ago?
My idea is that if people were fully rational we would still be living as we were before the discovery of electricity and modern chemistry. We would know that this is the only fully sustainable way of life on a finite planet and we would adhere to that except we could still have iPhones and breast implants, (Kidding)
It seems to me rationality is only half the problem. The other half is information. Without complete information about the consequences of activities you mention even the most rational person would not come to the conclusions you suggest. Your question does raise the issue of "What is the good life?" given the facts that the CC lays out. That may be worthy of another thread however. The question of rationality reminds me of the Dept of Agriculture in the New Deal. They set up "democratic discussion groups" and produced pamphlets on particular topics. The Ag Economists that created that program expected that group discussion would yield a consensus (that matched their own conclusions). This did not happen then.