Thank you for posting this example! I've used something like this myself to describe Set, but it didn't occur to me when I wrote my comment on the OP. The notio

Thank you for posting this example! I've used something like this myself to describe Set, but it didn't occur to me when I wrote my comment on the OP. The notion that one can quantify over properties (not just concrete objects) is one that is not necessarily obvious to someone without mathematical training.