Joseph W. Tkach was the appointed successor of Herbert W. Armstrong, founder of the Worldwide Church of God. Tkach became President and Pastor General of the church upon the death of Armstrong in 1986. Tkach spearheaded a major doctrinal transformation of the Worldwide Church of God, abandoning Armstrong's unconventional doctrines and bringing the church into accord with mainstream evangelical Christianity. His son, Joseph Tkach Jr., continued his work and in 1997 the Worldwide Church of God became a member of the National Association of Evangelicals.
During Tkach's tenure, the changes that he implemented stirred much controversy and significant dissent among those who continued to follow Armstrong's theology. The dissenters labelled the changes as heresy and many left to form new church organizations. Within the mainstream Christian community, some have hailed Tkach's reforms, which brought a church from the fringe to orthodoxy, as unprecedented in the history of the Christian church.
The first major change under Tkach's tenure was the WCG's doctrine on healing. Previously the church taught that true believers were healed by faith in God and not by doctors. Tkach asked the church leadership to study the question. Once Tkach was satisfied with the results of the study, he officially softened the church's teaching on the matter, encouraging members to seek proper treatment while retaining faith in God as healer.