W hen I (Jiansheng Guo) 2 rst went from China to Berkeley in 1986 to do my graduate stud-

ies in language acquisition, I was overwhelmed by Dan’s enthusiastic energy, charismatic warmth, expansive knowledge, and capacious heart and mind. His sharp insights and

never-ending interest in a wide range of intellectual issues across many disciplines were contagious, and forever exciting and stimulating. Dan consistently shows his students his trade-mark intellectual style by examining the issue from multiple directions and dimensions. He always approaches the understanding of language dialectically from both static and dynamic perspectives, never separating language use and language structure. He believes that “One cannot separate a theory of language change from a theory of language structure” (Slobin, 1977, p. 186). He begins with the research question about the universal character of language in language acquisition, but he addresses the issue ingeniously, by looking at the vast variations of languages and the dynamic nuances in language change and development. A philosophical and dialectical remark of his struck me in my rst year at Berkeley, and has been engraved in my mind ever since: “In a remarkable way, language maintains a universal character across all of these continuing changes, so that the more it changes, the more

sure we can be of what it is” (Slobin, 1977, p. 186). This motto has since inspired me to examine the complex and dynamic nature of any ostensibly simple and static phenomenon.