Joshua Fishman's pioneering academic work in the sociology of language aimed at examining the nature of language maintenance and shift and to build a scientific basis to back language activists who wanted to fight the seemingly inevitable evolutionary forces leading to the threat and loss of minority languages. Fishman's scholarly work covered many pioneering contributions to the inquiry of Yiddish sociolinguistics, but it extended to comprise not just other endangered languages but also to build a solid academic basis for researching what happens when stronger languages meet weaker.