Finally, then, it seems best to me to let the images and the shadows go, as being deceitful and very far short of the truth; and clinging myself to the more reverent conception, and resting upon few words, using the guidance of the Holy Ghost, keeping to the end as my genuine comrade and companion the enlightenment which I have received from him, and passing through this world to persuade all others also to the best of my power to worship Father, Son, and Holy Ghost, the one Godhead and power. To him belongs all glory and honor and might forever. Amen. (Gregory Nazianzus, Theological Orations, V.33).
A thing may be reasonably proved either by going to the root of the matter and producing a cogent demonstration…or by accepting it and then showing the consequences of the evidence…
The first method of proof is serviceable in dealing with such truths as God’s unity. But the second must be adopted when we would show forth the truth of the Blessed Trinity. We start with acceptance, and then afterwards mat give recommending reasons, not that they sufficiently demonstrate the mystery. (Thomas Aquinas, Summa Theologica, Ia.xxxii. 1)
Now over against all those who want to base the doctrine of the Trinity on rational grounds, we must undoubtedly maintain that we owe our knowledge of this doctrine solely to God’s special revelation. Scripture alone is the final ground for the doctrine of the Trinity. (Herman Bavinck, Reformed Dogmatics, II, 329).
The doctrine of the Trinity is presuppositional. That is to say, one cannot demonstrate the necessity or veracity of the doctrine from reason alone. Not only is it a supernatural dogma, it is a supra-natural doctrine, and as such can only be understood as it is supernaturally revealed by God in Scripture.
Gregory, Aquinas, and Bavinck all are saying the same thing: the Trinity is only first and compellingly known through Scripture. Though there are countless analogies, there are none that are adequate. As Gregory writes in the statement immediately preceding the above quote, “In a word, there is nothing which presents a standing point to my mind in these illustrations from which to consider the object which I am trying to represent to myself, unless one may indulgently accept one point of the image while rejecting the rest.” If there were a perfect analogy for the Trinity, the Trinity would not be perfectly unique. The Trinity would not be God.
To know what God wishes you to know about the Trinity, you need not plumb the depths of metaphysics, philosophy, mysticism, etc. God has revealed what you need to know about the Trinity in Scripture. You will never comprehend the Trinity: just as you will never comprehend the Father, or the Son, or the Spirit. But you will apprehend all God wishes you to know by studying the revelation of the Trinity in Scripture. While every text that says something about any of the Persons reveals something about the Trinity, there are multitudes of texts that speak of the Three. Search these texts out. Study them. Acquaint now thyself with God and be at peace.