[Superman]

Sounds like this is also part of the yin/yang thing. Or perhaps the male/female thing so prevalent in spanish cultures. To illustrate, what about a battering ram? It has no emptiness, and gets its usefulness from its density. An empty cup is useful for its capacity to accommodate. That's nice, but it represents only one set of purposes. There is at least one other set of purposes for which the ability to accommodate is not useful.