Why does protected inheritance cause dynamic_cast to fail?

Question

I changed my C++ base class to be protected inheritance and my dynamic_cast(s) stopped working.

Why should changing the inheritance to

Answer 1

Private (or protected) inheritance is semantically different from public inheritance. It is not a "is-a" relationship but a "implemented in terms of" relationship.

Meaning that you can't use a base class as a handle to a derived object.