An approach to resolving such difficulty is to use "predicates" as a general term for whether things are variously real, abstract, concrete, or of a particular property (e.g. "good"). Questions about the properties of things are then propositions about predicates, which propositions remain to be evaluated by the investigator. In the "graph 1" above, the graphical relationships like the arrows joining boxes and ellipses might denote predicates. Different levels of abstraction might be denoted by a progression of arrows joining boxes or ellipses in multiple rows, where the arrows point from one row to another, in a series of other graphs, say graph 2, etc.