> Afaict the difference between Smalltalk and Objective-C style message passing and Java and C# style method calling is purely syntactic.
doesNotUnderstand:/forwardInvocation: isn't different? That is not just syntactical. How would you even begin to orient your objects without like functionality?
I agree that if you squint really hard they look the same. But if we say "they are all the same", what are you trying to communicate when you say OOP? Virtually all programming languages we use have objects. You may as well drop the OO and just use "programming". It would communicate the same intent.