Q. I wanted to give my unsaved friend a clear definition of the trinity. But, the definition was so unclear in my dictionary that I gave up. What do you make of this theological dictionary's explanation of the trinity?
From a Dictionary
The trinity is:
The term designating one God in three persons. Although not itself a biblical term,…it is a convenient designation for the one God self-revealed in Scripture as the one essence of the Godhead. We have to distinguish three "persons" who are neither three gods on the one side, nor three parts or modes of God on the other, but coequally and coeternally God.
(Evangelical Dictionary of Theology).
You have my sympathy. There is a saying that "you can usually dodge a question with a long-winded answer." When it comes to defining the trinity, most theology books fit.
Scripture Defines Itself
John 1:1&John 10:30
So, rather than give your friend a long-winded definition of the trinity, you might try using Scripture to define Scripture.
Jesus said, "I and the Father are one" (John 10:30).
John 1:1 presents the "logos" statement, "In the beginning was the Word, and the Word was with God, and the Word was God" (ESV).
An Old Testament passage made famous by Handel's "Messiah" is: "For to us a child is born, to us a son is given, and the government shall be upon his shoulder, and his name shall be called Wonderful Counselor, Mighty God, Everlasting Father, Prince of Peace" (Isaiah 9:6, ESV).
Isaiah 7:14 reveals that …"the virgin shall conceive and bear a son, and shall call his name Immanuel." The word "Immanuel" means "God is with us."
Deuteronomy 18&Philippians 2
Deuteronomy 18:15-18 explains that the Israelites were terrified to witness God in the great fire or to hear the voice of the Lord anymore. So God promised to raise up for them "a prophet like me from among you."
From the New Testament book of Philippians, verses 2:5-7, we find it explained this way:
"Make your own attitude that of Christ Jesus, who existing in the form of God, did not consider equality with God as something to be used for His own advantage. Instead He emptied Himself by assuming the form of a slave, taking on the likeness of men…" (Phil. 2:5-7, HCSB).
C.S. Lewis explains that the Creator became one of His creatures. It is logical that for almighty God to communicate with the majority of human beings, He had to become one of us.
Matthew 28:19 - Last Words
Finally, Jesus' last words to us were:
"Go, therefore, and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit, teaching them to observe everything I have commanded you. And remember, I am with you always, to the end of the age" (Matthew 28:19-20, HCSB).
In the "Name" - not in the "Names"
The Life Application Study Bible notes explain it this way: "Jesus' words affirm the reality of the Trinity. Some people accuse theologians of making up the concept of the Trinity and reading it into Scripture. As we see here, the concept comes directly from Jesus himself. He did not say baptize them into the "names," but into the "name" of the Father, Son, and Holy Spirit. The word "Trinity" does not occur in Scripture, but it well describes the three-in-one nature of the Father, Son and Holy Spirit" (pg. 2041).
Most of us are not trained theologians. So it might be best to just stick with Scripture and use a good study bible.
Elwell, Walter A. 1984. Evangelical Dictionary of Theology, 2nd. Ed. Grand Rapids, MI: Zondervan.
Life Application Study Bible, NIV large print. 1991. Grand Rapids, MI: Zondervan.