However, they can easily be made asynchronous and address multiple recipients. See Higher Order Messaging[1][2], first implemented in Objective-C[3]. So for example:

    [[myView onMainThread] setNeedsDisplay:YES];

    result = [[someObject future] someMessage:arg];

    combined = [[prefixes collect] stringByAppendingString:[suffixes each]];

The reason this is easy in Objective-C is because its brand of message passing is just (barely) powerful enough to qualify as message passing. In fact, if you squint just a little, you can see it as fully reified message passing with the common-case (a synchronous method is invoked) optimized.

[1] http://en.wikipedia.org/wiki/Higher_order_message

[2] http://www.metaobject.com/papers/Higher_Order_Messaging_OOPS...

[3] https://github.com/mpw/MPWFoundation