Just to be clear, that's not in conflict with what the author claimed. You can't call that method using a pointer to the derived class. That would be an access

Just to be clear, that's not in conflict with what the author claimed. You can't call that method using a pointer to the derived class. That would be an access violation, because it was declared private. You need to use a pointer of the superclass type. struct I_A { virtual void foo() {} }; struct A : I_A { private: virtual void foo() {} }; int main() { A a; // a.foo(); // compile error I_A& ia = a; ia.foo(); // ok } To be honest, I find this behaviour useful so it doesn't upset me. It's a decent way to mark off functions that you needed to implement to satisfy an internal interface as not-for-users.