>>16
Yes, but what if some other guy comes with a new class, Vagina, for which there's no implementation of x, yet the Penis one would work because Vagina objects can behave like Penises (yet they don't inherit from any common class or anything like that; maybe Vagina doesn't even know about Penis)? In a dictionary-based type system, the system couldn't give a fuck (no pun intended) about what you pass as long as it happens to have the dictionary keys you ask for.