저자는 1949년 드레이크 대학(Drake University)을 졸업하였고, 피츠버그 액세니아 신학대학교에서 신학학사(B.D.) 학위를 받았다. 그는 목사로 장립받은 후 대부분 그의 사역은 뉴질랜드의 개혁 교회들과 그가 지속적으로 봉사하고 있는 정통 장로 교회(the Orthodox Presbyterian Church)와 함께하였다. 윌리암슨은 현재는 은퇴하였으며 목회자들, 장로들, 그리고 집사들을 위해 정통 장로교(the Orthodox Presbyterian Church) 에서 출판되고 있는 부름받은 종(Ordained Servant)의 편집자이다. 그는 The Westminster Shorter Catechism: For Study Classes 와 The Heidelberg Catechism: For Study Guide를 포함하여 개혁주의 기독교인들에게 좋게 인정 받아왔던 다른 저서들을 저술하였다. G. I. Williamson graduated from Drake University in 1949, and received the B. D. degree from pittsburgh-Xenia Theological Seminary in 1952. An ordained minister, he has served congregations in the Old United Presbyterian Church of North America, the Associate Reformed presbyterian Church, and the Reformed Presbyterian Church of North America. But most of his ministerial service has been with the Reformed Churches of new Zealand and the Orehodox Presbyterian Church, which he continues to serve. Now semiretired, Williamson is editor of Ordained Servant, a journal published by the Orthodox Presbyterian Church for pastors, elders, and deacons. He has written several other books that have been well received by Reformed Christians, including The Westminster Shorter Catechism: For Study Classes and The Heidelberg Catechism: A Study Guide. He is also edi- tor of The Wstminster Larger Catechism: A Commentary, by Johannes G. Vos.