Ideas are only useful if they imply actions. This includes "big ideas" and grand abstractions.
Corollary: political ideas and opinions are only worthwhile if they imply policies. If you can't use them to generate a policy, you are not thinking clearly. This includes political "big ideas" and grand abstractions. They must at least be able to imply actions, even if you are trying to abstract across various historical societies.
Ideas should be machines for generating actions, otherwise they are pointless.