Question: "How is the doctrine of the Trinity not tritheism?"
Answer: The doctrine of the Trinity is at the very center of the Christian faith. That God is triune in nature is affirmed not only in Scripture but also in the early ecumenical creeds of the church—specifically, Nicaea (A.D. 325) and Constantinople (A.D. 381). The doctrine is essentially that God is one in being while existing as three co-equal, co-eternal Persons, namely, God the Father, God the Son, and God the Holy Spirit.
One often-heard objection to the Trinity is that the doctrine logically entails tritheism (a belief in three gods). But is this criticism valid? Is Trinitarian theology at odds with the clearly taught monotheism of the Hebrew Scriptures? Or did the early Christians get it right when they upheld the monotheism of the Old Testament while at the same time affirming the full deity of three distinct Persons? To answer this question, we need to look over the biblical data. The Bible clearly affirms that there is but one God (Isaiah 43:10; 1 Corinthians 8:4). In addition, the Bible teaches the deity of the Father (John 6:27; Romans 1:7; 1 Peter 1:2), the Son (John 1:1-3; Hebrews 1:2; Titus 2:13; Colossians 1:16-17), and the Holy Spirit (Acts 5:3-4; 1 Corinthians 3:16). Moreover, the biblical writers go out of their way to affirm that all three Persons are distinct from each other (Matthew 28:19; Romans 15:30; 2 Corinthians 3:14). So, while it is true that the word trinity is not found in the Bible, the concept most certainly is.
Does the fact that there exist three divine Persons entail that there exist three separate gods? The answer is no. The same Scriptures that affirm that all three Persons of the Trinity are divine also unequivocally affirm monotheism (Deuteronomy 6:4; 1 Timothy 2:5). So, what are we to do with this tension between the idea of three divine Persons and monotheism? A helpful clarification involves what we mean by the word person.
Person can be defined as “a center of self-consciousness.” A person has a mind, emotions, and a will, can communicate with others, and is capable of performing actions. When we speak of the concept of personhood as it relates to the Trinity, we are describing self-distinctions in God. All three Persons of the one triune God possess the complete attributes of deity. All three Persons are truly divine, yet eternally distinct from one another. The divine Persons can and do communicate with each other (John 17:1-26; Hebrews 1:8-9). Essentially, God has three centers of self-consciousness. Yet this one Being (the triune God of Scripture) possesses one indivisible essence. There is only one Being that is God, and this one Being is tri-personal, with each of the three Persons having full possession of the divine nature.