The word "pietism" usually conjures up a host of ambivalent im pressions. It has seemed to me increasingly clear that many of the strengths of pietism have been swept aside by reactions against the excesses of the movement. To properly assess the structures of pietism, it is important to comprehend its matrix and to understand its ex ponents. In preparing this study, therefore, I have sought to recapture something of the person of Theodorus Jacobus Frelinghuysen as well as the gist of his thought; something of his environment as well as the institutions of his day. To achieve this I have traveled many by-paths and knocked on many doors. But the past has not always yielded its secrets; much is lost forever. Hagen in Westphalia, Frelinghuysen's birthplace, is now a modern city and only in a few isolated particulars is it reminiscent of Hagen in 1693. In the nearby village of Schwerte, however, the ancestral church of his forebears remains as it was nearly three hundred years ago. The gymnasium he attended in Hamm was destroyed in the bombings ofW orld War II, though the library he used during his study at Lingen is still largely intact. In the tiny East-Frisian village of Loegumer Voorwerk, Frelinghuysen's first parish, one can still stand in the pulpit where he first preached his awakening gospel. Yet oddly enough, in America, where his name is most remembered, most physical traces of his life have disappeared.