Unless a society is expecting its own future choices to be better than its present ones, it will strive to make its present policies and institutions as immutable as possible. Therefore Popper’s criterion can be met only by societies that expect their knowledge to grow – and to grow unpredictably. And, further, they are expecting that if it did grow, that would help.
This expectation is what I call optimism, and I can state it, in its most general form, thus:
The Principle of Optimism: All evils are caused by insufficient knowledge.