[meheleventyone]

I'd take all of those as receivers if they are reacting to a message being sent.

To give another example in a game engine I recently worked on we sent messages between game entities and the sending entity could target itself directly and indirectly with no problems and a common pattern to keep components of the entity decoupled was to do just that.

In some OOP languages the environment and everything else are all objects. I think Smalltalk itself works that way. Which reflects this way of thinking.