Frank Sheed’s book, Theology for Beginners, has a great explanation. I’ll give some lines from that book…
[pg 10]
God is a spirit …
[pg 55]
Spirit is a partless, spaceless, immortal being, which can know and love.
[pg 29] First, the three persons do not share the diving nature; it is utterly simple and cannot be divided up; it can be possessed only in its totality.
[pg 30] (Sheed goes on to say - “
they know with the same intellect, love with the same will.”)
[pg 31] We must, God aiding, bring our minds to bear upon that infinite act of generation by which God the Father begets his Son; and upon that infinite union in love by which the Holy Spirit proceeds from Father and Son.
[pg 33] But there cannot be two infinite natures - one would be limited by not being the other and by not having power over the other. Therefore, since the Son has infinite nature, it must be the same identical nature as the Father’s.
This truth, that Father and Son possess the one same nature, might remain wholly dark to us if St. John had not given us another term for their relation - the second person is the “Word” of the first.
[pg 33] So God utters a word - not framed by the mouth, of course, for God has no mouth. He is pure spirit. So it is a word in the mind of God… What idea produced in God’s mind could possibly be God? Christian thinking saw early that it could be only the idea God has of himself.
[pg 34] The link between having a son and having an idea of oneself is that both are ways of producing likeness. Your son is like in nature to yourself; your idea of yourself bears some resemblance to you too - though it may be imperfect, for we seldom see ourselves very clearly; too many elements in us we see as we wish they were, too many we do not see at all.
[pg 34] Whatever is in the Father must be in his idea of himself, and must be exactly the same as it is in himself… “In the beginning was the Word, and the Word was with God. And the Word was God.”
[pg 34] Men have ideas, and any given idea is something. God’s idea of himself is not something only; it is Someone, for it can know and love.
The thinker and the idea are distinct, the one is not the other, Father and Son are two persons. But they are not separate. An idea can exist only in the mind of the thinker; it cannot, as it were, go off and start a separate life of its own. The idea is in the same identical nature; we could equally say that the nature is in the idea, for there is nothing that the Father has which his Word, his Son, has not. “Whatsoever the Father has, that the Son has in like manner” (Jn 16:15). Each possesses the divine nature, but each is wholly himself, conscious of himself as himself, of the other as other.
[pg 35] Father and Son love each other, with infinite intensity. What we could not know, if it were not revealed to us, is that they unite to express their love and that the expression is a third divine person. In the Son, the Father utters his self-knowledge; in the Holy Spirit, the Father and Son utter thier mutual love.
[pg 36]
As the one great operation of spirit, knowing, produces the second person, so the other, loving, produces the third.
[pg 36-37]Observe that the third person is never spoken of as a Son, never said to have been begotten or generated. Theologians use the word “spirated” which is simply “breathed.” We may wonder why the third person who is the utterance of the love of Father and Son should be called their Breath.
Let us note two things. It is of universal experience that love has an effect upon the breathing; it is a simple fact that the lover’s breath comes faster. And there is a close connection between breath and life - when we stop breathing, we stop living. In the Nicene Creed the Holy Spirit is called “the Lord and giver of life.” The link between life and love is not hard to see, for love is a total self-giving, and so a giving of life.
[pg 45] A man with an idea in his head and love in his heart is one man, not three men. God, knowing and loving, is one God - even though the idea produced by his knowledge is a person, and the inward utterance of his love is a person; for as we have seen, the idea remains within the mind that thinks it, the lovingness within the nature that loves.
[pg 45] Theology has formulated the doctrine as “three persons in one nature.”
So, my answers to your questions:
- Who is he? He is the second person of the Trinity. (If you asked “What is he?”, I would say He is God and man.)
- What exactly does “son of god” mean? It means that His nature is in likeness to God’s nature.
- What does “he is god” mean? It means that He possesses the divine nature; not a part of divine nature, not a copy of divine nature, but the divine nature in total.
- What does “messiah” mean? Messiah is Hebrew for “the anointed one”.
- What does “word of god” mean? It means that He is an idea in the mind of God that God has of himself. Theologians have thought that it was appropriate for the “Word of God” to become man and save the word, because it was the “Word of God” can created the world (you know - God said “Let there be light” etc…).
