This book examines the language studies of Western missionaries in China and beyond. The goal of this study is to examine the purpose, methods, context, and influence of missionary language studies. The book reveals new insights into the hitherto less well-known and unstudied origins of language thinking. These publically unknown sources virtually form our «hidden history of language». Some key 17th century and pre-17th century descriptions of language not only pass on our Greco-Latin «grammatical» heritage internationally for about two millennia. They also reveal grammar, speaking, and language as an esoteric knowledge. Our modern life has been formed and influenced through both esoteric and common connotations in language. It is precisely the techniques, allusions, and intentions of language making revealed in rare, coded texts which have influenced our modern identities. These extraordinary and highly controversial interpretations of both language and Christianity reveal that our modern identities have been largely shaped in the absence of public knowledge and discussion.