This morning I have to confess right up front that I feel like I am engaging in an impossible task. When we talk about the doctrine of the Trinity we are really talking about that which we find impossible to fully comprehend. It's not that I don't think the doctrine of the Trinity is true. I believe it firmly. In fact, anyone who does not believe this doctrine, is a false believer. The reason the issue is difficult is because it is such a profound, mind boggling topic that it necessitates a level of understanding that humans do not possess..
Who hasn't had a child ask them: "Is Jesus God or is the Father God?" or "If Jesus is God, who was He praying to?" And I'm sure you can add your favorite question to the list. The three-in-one character of God is mind boggling. However, we affirm the doctrine of the Trinity for two really good reasons:
It is what the Bible teaches.
It is what the Church has affirmed through the centuries.
THE DOCTRINE DEFINED
The word "trinity" is not found in the Bible. But the concept of the Trinity is all over the Bible. The Westminster Confession states,
In the unity of the Godhead there are three persons, of one substance, power, and eternity: God the Father, God the Son, and God the Holy Spirit [Chap 2 sec. 3]
God is one in essence and three in person. In other words the Bible (and we) affirm that there is only One God . . .but this God exists in three "persons". We are saying that the Father is God, the Son is God and the Holy Spirit is God. They are not three gods but only one God. The Father is not the Son, the Son is not the Spirit, the Spirit is not the Father. They are distinct but one.
It's important to clarify. We are not saying there are three Gods. We are also not saying that God has three "forms" like steam, water, and ice. This is a heresy called modalism. In this heresy God is pictured as moving from one "mode" to the other. However, God is the Father, Son and Spirit at the same time and at all times. We are also not saying that the three persons of the Trinity are pieces of God. That would means that the Father was 1/3 God, the Son 1/3 God and the Spirit 1/3 God. There is one God . . . this one God exists in three persons: Father, Son and Spirit at the same time.
That's enough to give you a headache isn't it? Someone has rightly said "If you try to explain the Trinity, you will lose your mind. But if you deny it, you will lose your soul."
There are all kinds of analogies used to try to picture the Trinity. But there hasn't been a really good one yet. In fact, perhaps the most fun illustration is a pretzel. The story goes that a monk wanted to illustrate the Trinity so he took some dough and made it into the pretzel shape to denote the three in one. I don't know if the story is true . . . but it may help you think theologically as you eat your pretzels.
There are lots of other analogies, but none are very good. Perhaps the most helpful words I've read are those of C.S. Lewis,
A world of one dimension would be a straight line. In a two-dimensional word, you still get straight lines, but many lines make one figure. In a three-dimensional world, you still get figures but many figures make one solid body. In other words, as you advance to more real and more complicated levels, you do not leave behind you the things you found on the simpler levels: you still have them, but combined in new ways--in ways you could not imagine if you knew only the simpler levels.
Now the Christian account of God involves just the same principle. The human level is a simple and rather empty level. On the human level one person is one being, and any two persons are two separate beings- just as in two dimensions (say on a flat sheet of paper) one square is one figure, and two squares are two separate figures. On the Divine level you still find personalities; but up there you find them combined in new ways which we, who do not live on that level, cannot imagine. In God's dimension, so to speak, you find a being who is three Persons while remaining one Being, just as a cube is six squares while remaining one cube. [MERE CHRISTIANITY p. 137-138]
The Trinity is hard to grasp because we have nothing like it in our existence. God is higher and beyond our world but has to be described by human words that have limits.