[UntoHim]

Here is an excerpt from an article posted on John Piper's DesiringGod.Org site. I have bolded that parts that I feel are most applicable to our discussion here. I am not posting this article because I agree with every jot and tittle, but rather as a catalyst to maybe sharpen up our understanding of some of the rather esoteric theological terms being thrown around.

I personally favor starting with the lowest common denominator frequently enunciated as "God is three persons in one being". I favor the term "being" over "essence" for the simple reason being seems to be more personal, or subjective as it were. "Essence" seems to be a little more objective. I must say, however, I'm not willing to attempt to win the battle of semantics over these terms, and risk loosing the goal of the war, which is coming to the full knowledge of the truth regarding the nature, character and marvelous works of our wonderful, mysterious and glorious God.

What is the Doctrine of the Trintiy
Article by Matt Perman

Carrying this concept over to the Trinity, it is not a contradiction for God to be both three and one because he is not three and one in the same way. He is three in a different way than he is one. Thus, we are not speaking with a forked tongue — we are not saying that God is one and then denying that he is one by saying that he is three. This is very important: God is one and three at the same time, but not in the same way.

How is God one? He is one in essence. How is God three? He is three in Person. Essence and person are not the same thing. God is one in a certain way (essence) and three in a different way (person). Since God is one in a different way than he is three, the Trinity is not a contradiction. There would only be a contradiction if we said that God is three in the same way that he is one.

So a closer look at the fact that God is one in essence but three in person has helped to show why the Trinity is not a contradiction. But how does it show us why there is only one God instead of three? It is very simple: All three Persons are one God because, as we saw above, they are all the same essence. “Essence” means the same thing as “being.” Thus, since God is only one essence; he is only one being, not three. This should make it clear why it is so important to understand that all three Persons are the same essence. For if we deny this, we have denied God’s unity and affirmed that there is more than one being of God (i.e., that there is more than one God).

Essence and Person

Essence.
What does essence mean? As I said earlier, it means the same thing as being. God’s essence is his being. To be even more precise, essence is what you are. At the risk of sounding too physical, essence can be understood as the “stuff” that you “consist of.” Of course we are speaking by analogy here, for we cannot understand this in a physical way about God. “God is spirit” (John 4:24).

Person.
In regards to the Trinity, we use the term “Person” differently than we generally use it in everyday life. Therefore it is often difficult to have a concrete definition of Person as we use it in regards to the Trinity. What we do not mean by Person is an “independent individual” in the sense that both I and another human are separate, independent individuals who can exist apart from one another.

Wayne Grudem explains:
But if each person is fully God and has all of God’s being, then we also should not think that the personal distinctions are any kind of additional attributes added on to the being of God. . . . Rather, each person of the Trinity has all of the attributes of God, and no one Person has any attributes that are not possessed by the others. On the other hand, we must say that the Persons are real, that they are not just different ways of looking at the one being of God . . . the only way it seems possible to do this is to say that the distinction between the persons is not a difference of ‘being’ but a difference of ‘relationships.’ This is something far removed from our human experience, where every different human ‘person’ is a different being as well. Somehow God’s being is so much greater than ours that within his one undivided being there can be an unfolding into interpersonal relationships, so that there can be three distinct persons.
-