Smalltalk "messages" are not asynchronous, but they are also not "good old method calls." One example of that is that objects handle any message and if it does

Smalltalk "messages" are not asynchronous, but they are also not "good old method calls." One example of that is that objects handle any message and if it doesn't know how to reply by default (defined in Object class) it raises an error. But this can be redefined (message doesNotUnderstand:) to do anything you want.