Compared with prototypical universal quantifiers in other languages of the world, dou in Mandarin Chinese presents more complicated semantic behaviors. One of the most disputed issues is what are the relations between dou expressing “universal quantification” (uq) and dou expressing “scalar trigger” (sca). First-hand data that comes from 40 languages demonstrates that Mandarin Chinese is the only language that employs the same form for “universal quantification” and “scalar trigger”. The empirical evidence strongly suggests that uqdou and scadou are different, and the two functions uq and sca lack universal conceptual correlations. The special polysemous behavior of Mandarin dou, is proved to come from two language-specific reanalysis processes in dou’s diachronic development which also supports the two-dou claim. The study thus instantiates how a cross-linguistic perspective provides insights to explain long-standing language-particular issues. Besides, it is also argued that the cross-linguistic approach is promising in predicting if a future research is on a right track as it can steer us through overgeneralization and undergeneralization.