[lucifer]

A call is invoking a known method bound to the object. In a call based system, the semantics of the object are defined by its interface.

A message is invoking a universal message receiver method bound to all object. Semantics are determined by message content processing. (c.f. "meta boundaries").

It seems accurate then to say "message passing is a specialized form of method invocation that relies on a universal receiver method and delegates the invocation of object methods to the receiver.