The other day a Christian acquaintance stated: “To claim that the Father, Son, and Holy Ghost are all the same being is modalism which is false teaching.”
He’s exactly half right. Modalism is false but believing in only one being who is God is not Modalism. To further cloud his foggy mind, a well-meaning friend offered this unhelpful, albeit popular, analogy:
God is one, three persons in one…like water (liquid ), ice (solid), gas (moisture ) all three are [the] same, water…
The problem with this analogy is that it more closely resembles Modalism—the very error my friends are trying to refute—than Trinitarianism.
You see, Modalism is the idea that there is only one Person who is God. That is, Father, Son, and Holy Spirit are not persons; but are manifestations or modes of one person. The Modalist will say things like, “God is the Father in creation, the Son in redemption, and the Spirit in emanation.” (This is catchy but wrong.)
So you can see how the various modes of water (solid, liquid, or gas) correlate more to Modalism rather than to Trinitarianism.
However, in effort to avoid Modalism one mustn’t overcorrect into Tritheism by stating that Father, Son, and Holy Spirit are not the same Being.
Polytheism is no weapon against Modalism. Christian orthodoxy is.
The Christian faith acknowledges one God in three Persons. In other words, there is only one Being who is God and this one Being is eternally and immutably three coequal and coessential Persons: Father, Son, and Holy Spirit.
Being has reference to WHAT God is and Persons has to do with WHO God is. Thus, when we speak of the “One God who is Three,” we are not guilty of spouting logical absurdities. Rather, we are talking about God as being One in one sense and Three in another. ("The Forgotten Trinity," by James White is an excellent resource which makes this distinction clear.)
A better conception of One and Three comes to us from St. Augustine. He likens the Trinity to the unity/diversity of the mind: intellect, memory, and will. Another way to think on these things is the analogy of the space around us: light, heat, and air.
Is it any wonder C.S. Lewis said if we were making this up we would have made it simpler? To be sure there is mystery. But religion without mystery is religion without God.