Despair IS rational. AND despair is self-fulfilling. Both are true at the same time. The question is what you do when the rational response leads to the worst outcome. If we give up on the possibility of a collective turn, we guarantee failure. If we don't, the future remains non-zero.
The central paradox hinges on this: The question is not whether every belief is vindicated. The question is whether it is more rational to keep the door open or to slam it shut.
This is not about being optimistic. It is about whether it is still rational to believe that evolution may not be finished with us yet.