Nulling It Over

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Yes, this really is my father, posting in the comments section of Swampland:

“The set of purple horses is a null set. The set of Dick Armey’s intelligent insights is a null set. That’s two null sets. Not just one.”

In set theory, two sets are the same if they contain the same elements. The two sets you describe have the same elements (none). Said another way, every element of the first set is an element of the second set. And every element of the second is an element of the first. So your two descriptions define the same set – the null one.

As Crust wrote, I am writing about set theory, not measure theory. Perhaps some sort of measure theoretic model would allow your statement to be correct, but not set theory.

I was surprised to see Romney use a mathematical term, like the null set. But given that he did use the term, it is far more likely he meant the set theory null set, than measure theory ones.

Mathematical terms probably don’t belong here, but we didn’t start this.

He also knows a lot about insurance modeling and social security, maybe he’s interested in going over what Dick Armey has been discussing with Joe…