One of the first prominent countercult apologists was Jan Karel van Baalen (1890-1968), an ordained minister in the Christian Reformed Church in North America. His 1960 book, The Chaos of Cults, is a classic in the field.
Historically, one of the most important leaders of the movement was Walter R. Martin (1928-89), whose numerous books include the 1955 The Rise of the Cults: An Introductory Guide to the Non-Christian Cults and the 1965 The Kingdom of the Cults: An Analysis of Major Cult Systems in the Present Christian Era, which continues to be influential. He became well-known in conservative Christian circles through a radio program, "The Bible Answer Man," currently hosted by Hank Hanegraaff.
In his 1955 book, Martin gave the following definition of a cult, a definition that continues to be used within the movement:
As Martin's definition suggests, the countercult movement's emphasis has been on those groups that claim to be Christian, so chief targets have been the Church of Jesus Christ of Latter-day Saints, Jehovah's Witnesses, Christian Science and the Unification Church. The countercult movement at times also has spoken out against other religious movements that seem to be gaining popularity, such as the New Age movement, or against certain trends in society, such as the popularity of Harry Potter books.
Numerous other authors and Web site writers shape the movement today. Many of them target only one or two groups, often ones they have been disaffected with.
As would be expected in a diverse movement, not all countercult activists agree on which groups cross the boundary from being Christian to being a cult. Hanegraaff, for example, doesn't give the cult label to the Catholic church or the Seventh-day Adventist Church, although he says they have aberrant teachings. (Unlike most of the groups opposed by the movement, both Catholics and Adventists accept the traditional understanding of the Trinity.) Some countercult leaders have referred to both of those groups as cults because they are seen as obtaining some doctrines from places other than the Bible (Ellen G. White in the case of the Adventists, Christian tradition in the case of Catholics).
Hanegraaff also has been an outspoken opponent of what he calls word-faith teaching and the "holy laughter" movement, which he says are common in some Pentecostal circles. Prominent people in those movements include Rodney Howard-Browne, Paul Crouch, Benny Hinn and Kenneth Copeland. All of them emphasize the work of the Holy Spirit in a dramatic fashion, such as through glossolalia or faith healing; according to Hanegraaff and some others in the Christian countercult movement, those leaders often teach concepts that aren't in the Bible.