* message passing in Smalltalk is implemented as method invocation (the same is in Java, C#, C++, ...)
* encapsulation in Smalltalk: all fields are private/hidden (but: all methods are public)
This only seems true for the case of simply defined methods. Differences arising from being able to do late binding is better described on Dynamic Dispatch wiki page[0].
[0] https://en.wikipedia.org/wiki/Dynamic_dispatch#Dynamic_dispa...