If I needed an apology for endeavoring to show the reasonableness of this doctrine, it would be that in our day it is famentably true that the great body of so-called Christians, who have cast off the primary authority of revealed truth, and set up the destructive theory of private judgment in its stead, are fast losing their faith in this necessary truth of Christianity, and falling away into Rationalism and Infidelity. It becomes the Christian preacher, therefore, to raise his voice in defence of this fundamental doctrine of Christianity. Christianity is true only because the Trinity is true. Abandon that, and belief in Christ the incarnate Son of God is impossible.
Let us consider, then, with all due reverence, the mystery of the being of God, and express the reasons which our own mind can present to confirm the faith of the Christian, when, signing himself with the sign of Christ, he adds the solemn declaration of his belief in God, the Father, the Son, and the Holy Ghost.
First of all, it is proper to state distinctly what the doctrine of the Trinity is. We believe that there is one infinite, eternal Being, whose nature is in no way divided, nor can be conceived of as partly one thing, and partly another thing. We believe that God, though one in being, is a Trinity in person. This Trinity of person in God does not separate His being into parts any more than His attributes, such as His wisdom or His justice, could divide Him, making His wisdom or justice one thing, and Himself another thing, which is not wisdom or justice.
It is God who is both wise and just, and His wisdom and justice have no existence but in Him. So it is God, one Being, who is Father, Son, and Holy Ghost, and these three Persons, taken together, or one by one, are not something else besides the being of God, but they, each and all, are God. God is the Trinity. So that the Father cannot regard the Son, or the Holy Ghost, as some other being—some other God, because the Son and the Holy Ghost are the same God as the Father is. In being God is not three, but one. Nor does the fact of there being three Persons add anything to the being of God, or lessen the absolute perfection of His unity, by introducing an element of division: on the contrary, we shall see that a perfect being must exist in three persons, and a being with only one person, such as we are, is necessarily an imperfect being.
And when we say that the three Persons are distinct one from the other, so that the Father is not the Son, nor the Son the Holy Ghost, that again in no manner can affect the unity of the Divine Being, which in all three is identically the same. God, whose being is one, lives in three persons, and we can address ourselves to any one of the three separately, to God living as the Father, to God living as the Son, or to God living as the Holy Ghost; but the Being who lives, either as Father, or as Son, or as Holy Ghost, is One, and cannot be addressed in any manner as if He was double or triple. This very reasonable distinction between a being and the person of that being seems to be something which many wise and learned men appear either unable or unwilling to understand.
The being of God lives. He is the living God, and the three persons are His life. Not that God has three different lives; that as Father he has one life, and as the Son a second life, and as the Holy Ghost a third life. There is but one life in God, and it is the three persons that live that life. This appears to me to be the most reasonable explanation of the Trinity which our minds are capable of conceiving, and I will develop this thought in a few words.
God is a living being. Let us ask ourselves whence does God receive the life of His Divine Being? Who is the author of His life? Plainly, from no one but from Himself. He is the first, and only, and complete cause of His own life. There was nothing before Him from which He drew His infinite being, nor upon whose prior existence He depends for life. There is nothing now that can sustain Him or support His life, neither can there be anything after Him. He is the eternally living God. He is, then, the eternal cause of His own life.