I dreamed of empty sets. I had two null sets in front of me, so to speak. One set contained real apples that were not fruits and the other contained married bachelors. Trigo argued in his usual calm way that the sets were equal, stating the obvious truth that neither had any elements and therefore held the same number of elements. I argued that the sets could not possibly be equal because what one set lacked was not the same as what the other set lacked.

“Are you saying, my dear dog Trigo, that a married bachelor is equivalent to an apple that is not a fruit?”

“Yes, that is exactly what I am saying,” said Trigo.