At a bare minimum, understanding entails being able to detect an internal contradiction: a paradox.
Chapter 1: "Paradox", p. 21
The best paradoxes raise questions about what kinds of contradictions can occur—what species of impossibilities are possible.William Poundstone
Carl Friedrich Gauss, often rated the greatest mathematician of all time, played the market. On a salary of 1,000 thalers a year, Euler left an estate of 170,587 thalers in cash and securities. Nothing is known of Gauss's investment methods.William Poundstone
The assumption that anything true is knowable is the grandfather of paradoxes.William Poundstone
Are there any mythical beasts which aren't simple pastiches of nature? Centaurs, minotaurs, unicorns, griffons, chimeras, sphinxes, manticores, and the like don't speak well for the human imagination. None is as novel as a kangaroo or starfish.William Poundstone
"Average" isn't so hot at the race track given those steep track takes. "Average" is pretty decent for stocks, something like 6 percent above the inflation rate. For a buy-and -hold investor, commissions and taxes are small.William Poundstone