This is something that's bugged me for quite a while and I can't seem to get my head around it.
I constantly see things which, to my mind, seem to contradict, sometimes God is referred to as part or the whole of the Holy Trinity, but then in the Creeds, we profess that we believe in one God.
In short, I struggle with the idea of 3-in-1 and 1-in-3 aspect of God
the
Father, and the
Son, and the
Holy Spirit intimate a divine unity of one and the same substance in an indivisible equality; and therefore that they are not three Gods, but one God: although the Father has begotten the
Son, and so He who is the Father is not the Son; and the Son is begotten by the
Father, and so He who is the Son is not the Father; and the
Holy Spirit is neither the Father nor the
Son, but only the Spirit of the Father and of the
Son, Himself also co-equal with the Father and the
Son, and pertaining to the unity of the Trinity. Yet not that this Trinity was born of the
Virgin Mary, and crucified under
Pontius Pilate, and buried, and rose again the third day, and ascended into heaven, but only the Son. Nor, again, that this Trinity descended in the form of a dove upon Jesus when He was
baptized; nor that, on the day of Pentecost, after the ascension of the Lord, when there came a sound from heaven, as of a rushing mighty wind, the same Trinity sat upon each of them with cloven tongues like as of fire, but only the
Holy Spirit. Nor yet that this Trinity said from heaven, You are my Son, whether when He was
baptized by John, or when the three
disciples were with Him in the mount, or when the voice sounded, saying, I have both
glorified it, and will glorify it again; but that it was a word of the Father only, spoken to the Son; although the
Father, and the
Son, and the
Holy Spirit, as they are indivisible, so work indivisibly. This is also my
faith, since it is the
Universal Faith.
+ St Augustine
37. I
know, O Lord God Almighty, that I owe You, as the chief duty of my life, the devotion of all my words and thoughts to Yourself. The gift of speech which You have bestowed can bring me no higher reward than the opportunity of service in preaching You and displaying You as You are, as Father and Father of God the Only-begotten, to the world in its blindness and the
heretic in his rebellion. But this is the mere expression of my own desire; I must
pray also for the gift of Your help and compassion, that the breath of Your Spirit may fill the sails of
faith and confession which I have spread, and a favouring wind be sent to forward me on my voyage of instruction. We can trust the promise of Him Who said,
Ask, and it shall be given you, seek, and you shall find, knock, and it shall be opened unto you Luke 11:9; and we in our want shall
pray for the things we need. We shall bring an untiring energy to the study of Your Prophets and Apostles, and we shall knock for entrance at every gate of hidden
knowledge, but it is Yours to answer the
prayer, to grant the thing we seek, to open the door on which we beat. Our minds are born with dull and clouded vision, our feeble
intellect is penned within the barriers of an impassable
ignorance concerning things Divine; but the study of Your revelation elevates our
soul to the comprehension of sacred
truth, and submission to the
faith is the path to a certainty beyond the reach of unassisted reason.
38. And therefore we look to Your support for the first trembling steps of this undertaking, to Your aid that it may gain strength and prosper. We look to You to give us the fellowship of that Spirit Who guided the Prophets and the Apostles, that we may take their words in the sense in which they spoke and assign its right shade of meaning to every utterance. For we shall speak of things which they preached in a
mystery; of You, O God Eternal, Father of the Eternal and Only-begotten
God, Who alone art without birth, and of the One Lord
Jesus Christ, born of You from everlasting. We may not sever Him from You, or make Him one of a plurality of Gods, on any plea of difference of nature. We may not say that He is not begotten of You, because You are One. We must not fail to confess Him as
true God, seeing that He is born of You,
true God, His Father. Grant us, therefore, precision of language, soundness of argument,
grace of style, loyalty to
truth. Enable us to utter the things that we
believe, that so we may confess, as Prophets and Apostles have taught us, You, One God our Father, and One Lord
Jesus Christ, and put to silence the gainsaying of
heretics, proclaiming You as
God, yet not solitary, and Him as
God, in no unreal sense.
+ St Hilary of Potiers
By the way, several books have been written on this topic alone. Why don't you read some of the writings of the earliest Christians on the Holy Trinity if you really desire to have a more perfect understanding of this dogma?