Modalism, as known as Sabellianism (and Modalist Monarchianism), is a heresy that denies the Holy Trinity and asserts that the Three Persons of the Holy Trinity are mere modes of one divine Person. Orthodoxy Christianity, to contrast, believe that the One Triune God consists of three distinct persons, all co-equal and co-eternal. Modalists believe, to put in other words, that there is only One Person, who manifests himself in three different ways and at different times. The term Sabellianism comes from a priest who adopted the heresy in the 3rd Century AD, although it might predate Sabellius by the teaching another heretic, Noetus.
Modalism, Sabellianism, and Modalist Monarchianism were ruled heretical by the Councils of Nicaea and Constantinople and have been almost universally condemned as heretics by each major branch of orthodox and schismatic Christianity, including Protestantism, Catholicism and Eastern Orthodoxy. More so than any other heresy, this one is the most widely repudiated throughout the history of the Christian church.
Modern proponents of this heresy include Oneness Pentecostals, Unitarians, or others who use the term “Oneness” or “Jesus Only.” Despite vague denials, the most famous adherent to Modalism is the Prosperity Gospel and Word-Faith teacher, TD Jakes, whose official doctrinal statement is implicitly Modalist in nature, speaking of the Triune God as one God “in three manifestations.” This false doctrine is also affirmed by popular Contemporary Christian Music group, Phillips, Craig and Dean.