Ramarren, Banks added on that part later, and it renders a lot of the earlier books nonsensical - why didn't the Culture or the Idarans increase their intelligence to win their war, if it was that easy? I refuse to regard Excession as canon; it never happened.

Eh? Subliming doesn't help you win wars. It may or may not grant superintelligence and various other god-tier powers, but for balance reasons it also makes you stop caring about this universe, and you drift off into ... well, nobody knows.

OTOH, not only have the Minds have deliberately engineered their society so vast numbers of humans commit suicide when "their time is up", but "infinite fun space" is implied to contain entire civilizations, simulated down to the quantum level, so ... screw the Culture. Seriously.