AlmosteveryoneinChinaknowsthisstory,evenelementaryschoolpupils:Onceuponatime,therewasaweaponsalesmanclaimingwithconfidencetoonecrowdthatallhisspearswerecapableofpiercingeveryshieldthatexistedintheworld,thenheturnedaroundandtoldtheothercrowdmysteriouslythatallhisshieldswerenotpenetrable.Abystanderwhoheardbothclaimsaskedhim,"Howaboutstabbingyourshieldswithyourspears?"Itwasindeedanunexpectedquestionthatmadetheeloquentsalesmanmuterightonthespot.Sincethen,theChinesepeoplehavecalledcontradictionas"mao-dun",whichliterallymeans"thespear(pronouncedas"mao")andshield(pronouncedas"dun")".
