How can there be one God but three persons in the Godhead?

Q. How can there be one God but three persons in the Godhead, i.e. Father, Son, and Holy Spirit?

A. I so appreciate these questions about who (and what) God is because people can speak of
“God” but mean something totally different than the way God defines and explains himself. If I
want to speak of a tree, but define and explain it as an animal that walks on four legs, has a tail,
and barks you would quickly let me know that I’m not talking about a tree, but about a dog. It’s
the same (with very serious consequences) when people speak about “God” but do not
understand or do not accept what God tells us about himself. To make up our own definition of
“God” is both to disrespect God’s own self-description and to create an idol with our
imaginations. Be sure your view of God is not an idol of your own or someone else’s making.
The Bible is our sourcebook to tell us who and what God is precisely because it is God’s
Word. In last week’s Haven Heart to Heart we showed how the Word of God teaches that God
is three persons: Father, Son, and Holy Spirit - as you rightly state in your question.
But isn’t God one? “Hear, O Israel, the Lord our God, the Lord is one” (Deuteronomy
6:4). Cults that deny the Trinity, e.g. Jehovah’s Witnesses, emphasize this text, as do Muslims.
The Qur’an, the holy book for Muslims and for the religion of Islam uses this text to condemn the
Christian belief in the Trinity:
“Say not “Trinity”. Desist. It will be better for you: for God is one God. Glory be to Him:
(far exalted is he) above having a son.” Qur’an, Surah 4.171

So how do we fit the Trinity into God’s own statement that He is one?

1. Deuteronomy 6, where this affirmation is made, is about the uniqueness of God as
the One to whom alone we are to be devoted. So, Deuteronomy 6:5 goes on to tell us that we
are to love the Lord our God with all our heart, all our strength, all our soul, and all our mind.
This can only be done by knowing that there is one true and living God and by devoting
ourselves solely to him.

2. The Hebrew word for “one” in Deuteronomy 6:4 is not a word used for mathematical
singularity. Interestingly, it’s used Genesis 2:24 to speak of Adam and Eve - two distinct
persons - as one flesh. This background to the use of the term (remember that the Bible is to
interpret the Bible) shows that there can be a plurality that is still a unity. This great mystery
demonstrated in our first parents is also displayed in Jesus Christ and His Church, which is the
great reality of which the marriage of two persons is to be a reflections (Ephesians 5:30-32).
The fact of the matter is that everything in creation is, in one way or another, unity and
plurality. You can’t correctly understand the universe unless you realize that it was the Triune
God that created it. But we’ll need to open that up (and other practical implications of the
doctrine of the Trinty) next week.