How do you think John's people-or our society-can avoid repeating the mistakes that led to the distruction of civilization in the story?
This is a really tough question, but one that our own society is (sort of) facing right now (with the possibility that we are causing global warming that could have lasting impacts on civilization in the future. So I guess I'd think about it in those terms -- how could we make ourselves stop global warming?
To me, the only possible way to do this is through education. In John's case, he would have to go back to his people and say "look, these were people too and we can learn to be just like them. But at the same time, look what they did to themselves. We have to realize that that could happen to us too."
The problem for us (whether it be nuclear weapons or global warming) is that we don't have an example like John has. We can't say "look what happened to them -- don't let it happen to us." Even so, I think that the only way to do it is still through education. We have to convince people that technology can have a downside if we do not think a lot about how to use it and what the consequences of using it are.
We can only prevent ourselves from making mistakes by being as aware as possible about what bad things might happen. That can only come through education, in my opinion.