If you limit yourself to humans, yes. But at least one mind has to be able to think a thought for that thought to exist.
Ah, I thought you were limiting yourself to humans, given your example.
If you're asserting that for every pair of cognitive systems X,Y (including animals, aliens, sufficiently sophisticated software, etc.) if X thinks thought T then Y is capable of thinking T, then we just disagree.
Here's the new thread for posting quotes, with the usual rules: