The map is not the territory. We discuss reality on many levels, but there is only one underlying level. Justice, duty and the like are abstractions; we use the same symbol in multiple places to define certain patterns. You don't get two identical 'happinesses', like you get two identical atoms. It's useful for us though, to talk about this abstraction at the macro level and not the micro, and it's meaningful, given that we're assuming the same axioms. I think, stuff that causes other stuff is reality, and if we assume certain axioms that correspond to reality, any new truthful statements and concepts deduced are meaningful because they also correspond to reality. Everything there is covered. Things that exists, and things we think exists.