From everything I've read, it seems that Object does not need to be concrete, and in fact should have been abstract.
Not only is there no need for it to be concrete, but after some more reading I am convinced that Object not being abstract is in conflict with the basic inheritance model - we should not be allowing abstract subclasses of a concrete class, since subclasses should only add functionality.
Clearly this is not the case in Java, where we have abstract subclasses of Object.
