From the Reformer
In the gospel of St John, chapter three, is plainly and directly shown the difference of the persons, in the highest and greatest work that God accomplished for us poor human creatures, in justifying and saving us; for there it is plainly written of the Father, that he loved the world, and gave to the world his only begotten Son. These are two several persons—Father, and Son. The Father loves the world; and gives unto it his Son. The Son suffers himself to be given to the world, and “to be lifted up on the cross, as the serpent was lifted up in the wilderness, that whosoever believed in him shall not perish, but have everlasting life.” To this work comes afterwards the third person, the Holy Ghost, who kindles faith in the heart through the Word, and so regenerates us, and makes us the children of God.
This article, though it be taught most clearly in the New Testament, yet has been always assaulted and opposed in the highest measure, so that the holy evangelist, St John, for the confirmation of this article, was constrained to write his gospel. Then came presently that heretic, Cerinthus, teaching out of Moses, that there was but one God, and concluding thence that Christ could not be God, or God man.
But let me stick to God’s Word in the Holy Scripture, namely, that Christ is true God with God the Father, and that the Holy Ghost is true God, and yet there are not three Gods, nor three substances as three men, three angels, three sons, three windows, etc. No: God is not separated or divided in such manner in his substance, but there is only and alone one divine essence, and no more.
Therefore, although there be three persons, God the Father, God the Son, and God the Holy Ghost, yet notwithstanding, we must not divide nor separate the substance, for there is but only one God in one only undivided substance, as St Paul clearly speaks of Christ (Col 1:15-20), that he is the express image of the invisible God, the first born of all creatures; for through him all things are created that are in heaven and on earth, visible, etc., and all is through and in him created, and he is before all, and all things consist in him.
Now what the third person is, the holy evangelist, St John, teaches, chap. xv., where he says: “But when the Comforter is come, which I will send unto you from the Father, the Spirit of truth which proceeds from the Father, he shall testify of me.” Here Christ speaks not only of the office and work of the Holy Ghost, but also of his substance and faith; he goes out or proceeds from the Father, that is, his going out, or his proceeding, is without all beginning, and everlasting. Therefore the holy prophet Joel gives him the name, and calls him, “the Spirit of the Lord.”
Now, although this article seem strange or foolish, what matters it? `tis not the question whether it be so or no, but whether it be grounded on God’s Word or no. If it be God’s Word, as most surely it is, then let us make no doubt thereof; He will not lie; therefore, let us keep close to God’s Word, and not dispute how Father, Son, and Holy Ghost can be one God; for we, as poor wretches, cannot know how it is that we laugh; or how with our eyes, we can see a high mountain ten miles off; or how it is, that when we sleep, in body we are dead, and yet live. This small knowledge we cannot attain unto; no, though we took to our help the advice and art of all the wise in the world, we are not able to know the least things which concern ourselves; and yet we would climb up with our human wit and wisdom, and presume to comprehend what God is in his incomprehensible majesty.
—Martin Luther, Table Talk, “Of Idolatry”
Pulling It Together
The Godhead is one more item about God the Church must accept on faith. It seems foolish to many because there is nothing in the earthly experience that parallels it. It should not be surprising that God is so different from what is familiar. God is not of this earth. One may expect to encounter things here that indicate the divine but should never expect an explanation of his being. The latter requires revelation, which he has provided this in the Word.