Misunderstandings of the Trinity

Monergism has a helpful entry from the ESV Study Bible.

Common Errors:

• Tritheism: Overemphasizes the distinction between the persons of the Trinity and ends up with three gods.
• Modalism:(also known as Sabellianism, named after its earliest proponent, Sabellius, 3rd century), which loses the distinctions between the persons and claims that God is only one person. In this view, the appearance of the three persons is merely three modes of existence of the one God. For instance, God reveals himself as Father when he is creating and giving the law, as Son in redemption, and as Spirit in the church age (found in the teaching of Oneness Pentecostalism).
• Arianism (after a teacher named Arius, c. a.d. 256–336), and it is held today by Jehovah’s Witnesses: to deny the full deity of the Son and of the Holy Spirit, and to say that they were at some time created. This is the heresy of

Practical Implications of the Trinity

1. The doctrine of the Trinity makes definitive revelation of God possible as he is known in Christ:

(John 1:18). (Ex. 33:20; 1 Tim. 6:16)

2. The Trinity makes the atonement possible.

(Heb. 9:14).

3. Because God is triune, he has eternally been personal and relational in his own being, in full independence from his creation.

(Acts 17:25).

4. The Trinity provides the ultimate model for relationships within the body of Christ and marriage (1 Cor. 11:3; 12:4–6; Eph. 4:4–7).

From the Summary:

The doctrine of the Trinity is well beyond human ability to ever fully comprehend. However, it is central to understanding the nature of God and the central events in the history of salvation, in which God is seen acting as, in effect, a tripersonal team. Biblical Christianity stands or falls with the doctrine of the Trinity.