What does it mean that the Trinity is three in person but one in essence?

FERGUSON: By one essence, we mean that God is one being. The word essence comes from the Latin verb esse, “to be,” so what we mean is that He is one being. When we speak about Him as being three persons, the best way to understand the approach the early church had is this: God made us in His image, and because we are His image, there are things about our lives and our world that reflect who He is and what He is like.

We have the privilege of using language that is terrestrial because we have no other language. This is legitimated by the fact that we are made in the image of God to speak about Him. When we use that language, in a sense, there is a connection between us because we are His image. We are persons. We see in Scripture that there are many statements about God that are what we would call “personal.”

When the early church spoke in these terms, it was seeking to use terrestrial language to describe the celestial, but in such a way that was defined by God Himself and not by our experience of the vocabulary or our dictionary definition of the vocabulary. When we say that God is a person, we recognize that we are persons, but we are the microcosm—we exist in bodily form on the earth. From that, we also understand that God is a person. In other words, what makes us a person reflects that which is true of God but is not identical with what is true of Him.

All of our language about God is like this. It’s the language of those who are the analogy of God. We use that language and we have no other language to use. The language of analogy is legitimated by the dynamic that we are made in the image of God, but we are always recognizing that He’s given us the privilege of using language that enables us to know Him without totally comprehending Him. That is what those early theologians meant when they spoke about the incomprehensibility of God, but at the same time insisted on the wonder that the God we know is the incomprehensible God. We don’t know God as He knows Himself, but we do really know the One who knows Himself.

All of our theological language is of this analogical order, legitimated by the fact that we are made in the image of God. This is why it’s so important for us not to begin with ourselves and then to impose that language on God, but to realize that God has imprinted Himself into our lives and our world. That legitimates the vocabulary that’s born in this world but is a bridge to that world so that we may really know Him.

All knowledge of persons is like this. Derek and I have been close friends for a long time. We really know each other, but Derek is still incomprehensible to me.

THOMAS: It is mutual.

FERGUSON: I cannot fully understand who Derek is. Only he knows—and he only knows part of it—yet I still know him. I still have this relationship of brotherly affection, friendship, and trust with him. In a way, what we find in the knowledge of the Person of God is that same thing wonderfully magnified. We know Him, but the more we know Him, the more we say, “You are incomprehensible to me.”

When I see a young man in a wedding about to pledge himself forever to a woman, and I can see in his eyes the thought, “No man has ever known and loved a woman the way I know and love this woman,” I stand there thinking, “Come back in two years’ time and you’ll tell me that you had no idea who she was.”

When you’ve been married the length of time that many of us have been married, you’re still able to say, with a smile, that your wife is still incomprehensible to you. That doesn’t mean you don’t know her, but you realize that there are depths and mysteries to this other person because you’re not that other person. How much more, then, with the Lord. It’s wonderful when it’s true of your wife because of the fellowship that you have with her, and it’s even more wonderful when it’s the Lord because He is even greater than your wife.

PARSONS: I can’t wait to go home and tell Amber that she’s incomprehensible to me and that Dr. Ferguson said I could say that to her.

FERGUSON: Amen.