rails 3.0: ActionController::Base render()

Can anyone explain where render() comes from in ActionController::Base? I managed to trace it down only that far: ActionController::Base includes ActionController::Rendering where render() method is defined. This definition however calls to render of the superclass. Superclass is ActionController::Metal. Which in its turn inherits from AbstractController::Base. None of those have render () either defined or included.

Now, presumably it comes from AbstractController::Rendering, but I'm really missing how it gets included.

Thanks, Artem.