It must however be admitted that the names of these Divine Persons imply some closer union between them than that of merely possessing in common one Divine Nature. For they are not independent names like those of different men or of heathen gods, each of whom might exist separately; but they are all relative names, each implying the others. Thus the Father implies the Son, for how can there be a Father, unless there is a Son (or at least a child)? And of course an Eternal Father implies an Eternal Son, so any idea that the Father must have lived first, as in the case of a human father and son, is out of the question. Similarly the Son implies the Father, and the Spirit implies Him whose Spirit He is. And though these names are no doubt very inadequate; they yet show that the three Persons are of the same Nature, which is the important point.
We conclude then that the Doctrine of the Trinity means the existence of three Divine Persons, each possessing in its completeness the one Divine Nature; and closely united together; though in a manner, which is to us unknown.
(2.) Its credibility.
Having now discussed the meaning of the Christian doctrine, we have next to consider whether it is credible. It must of course be admitted that the doctrine is very mysterious, and though fairly intelligible as a doctrine, is extremely hard to realise (indeed some might say inconceivable) when we try to picture to ourselves what the doctrine actually means. But we must remember that the nature of God is anyhow almost inconceivable, even as simple Theism. We cannot picture to ourselves a Being Who is omnipresent,—in this room, for instance, as well as on distant stars. Nor can we imagine a Being Who is grieved every time we commit sin, for if so, considering the number of people in the world, He must be grieved many thousands of times every second; as well as being glad whenever anyone resists sin, also, let us hope, several thousand times a second. All this may be true, just as the marvels of science—the ether, for instance, which is also omnipresent, and has millions of vibrations every second—may be true, but our minds are quite unable to realise any of them.
Thus, as said in [Chapter III.], though we have ample means of knowing what God is in His relation to us as our Creator and Judge, yet as to His real nature we know next to nothing. Nor is this surprising when we remember that the only being who in any way resembles God is man; and man's nature, notwithstanding all our opportunities of studying it, still remains a mystery.
Now Christianity does attempt (in its doctrine of the Trinity) to state what God is in Himself, and without any reference to ourselves, or to nature; and that this should be to a great extent inconceivable to our minds seems inevitable. For the nature of God must be beyond human understanding, just as the nature of a man is beyond the understanding of animals; though they may realise what he is to them, in his power or his kindness. And for all we know, Trinity in Unity, like omnipresence, may be one of the unique attributes of God, which cannot be understood (because it cannot be shared) by anyone else. Therefore the mysteriousness of the Christian doctrine is no reason for thinking it incredible.
Nor is it inconsistent with Natural Religion, for though this shows the Unity of God, it is only a unity of outward action. It does not, and cannot tell us what this one God is in Himself, whether, for instance, He exists as one or more Persons. In the same way (if we may without irreverence take a homely illustration) a number of letters might be so extremely alike as to show that they were all written by one man. But this would not tell us what the man was in himself, whether, for instance, he had a free will, as well as a body and mind; or how these were related to one another. Hence Natural Religion can in no way conflict with Christianity.
(3.) Its probability.
But we may go further than this, and say that the Christian doctrine of Three Divine Persons is (when carefully considered) less difficult to believe than the Unitarian doctrine of only One. For this latter leads to the conclusion, either that God must have been a solitary God dwelling alone from all eternity, before the creation of the world; or else that the world itself (or some part of it) must have been eternal, and have formed a kind of companion. And each of these theories has great difficulties. Take for instance the attributes of Power and Wisdom, both of which, as we have seen, must of necessity belong to God. How could a solitary God dwelling alone before the Creation of the world have been able to exercise either His Power or His Wisdom? As far as we can judge, His Power could have produced nothing, His Wisdom could have thought of nothing. He would have been a potential God only, with all His capacities unrealised. And such a view seems quite incredible.