Why can't this method take derived class?

CornedBee, Ha Ha!!
In case of my brain, it goes via ears and eyes

PS: I can see CornedBee coming holding a Lock and Key!!!

Originally Posted by CornedBee

Or at least the bone is so thick that nothing can get through.

One should strive for such a skull, should they not? At least someone who doesn't want objects to penetrate it.

But all arguments aside, conceptually I see a Vector as what the STL describes it as, a Container. A Container which holds types. Some of those types may be pointers to types, but that distinction doesn't affect what a Vector is conceptually.