During the evangelization of Ireland, St. Patrick in striving to make understandable the mystery of the Trinity is said to have picked up a clover plant, pointed to the three lobes indicating that it was one plant.
The Church understanding of the Trinity has developed over the centuries but is stated its briefest form as follows:
in Three Divine Persons,
the FATHER, SON and HOLY SPIRIT.
How are we envision the One God?
One God: We speak of ONE NATURE, ONE SUBSTANCE, ONE BEING, Etc. This is all well and good but these concepts of natural theology fail to explain what causes the unity of the Trinity. If we listen to Christ who said: "The Father and I are One."(Jn 10:30) "I Am in the Father and the Father is in me."(Jn 14:10) " It is the Father who lives in me accomplishing his works.(Jn 14:10) we perceive a union unimaginable in creatures. Jürgen Multman says that by their eternal love the Divine Persons live and dwell in one another to such an extent that THEY ARE ONE.
The concept of "person" as it applies to human beings means an individual substance in a rational nature. In God, however, this individuation arises from the different relations to its origin. So the Son is generated by the Father from all eternity and so is distinct from the Father. And the Spirit originates from the Father and the Son from all eternity and is thereby distinct from them.
God as Father denotes that He is the origin of all things and that He exercised loving care over all his creatures. God's parental care can also be expressed by the image of motherhood but we must remember that God is neither Mother nor Father in the human sense. "No one is Father as God is Father".14
In God's providential care, Jesus uses the concept of Father rather than Mother to identify the First Divine Person. Jesus as a Divine Person, who with the First Person and the Spirit creates the reality of fatherhood and motherhood, has a profound understanding of creation. He chose the image of Father to represent the First Person since this image-concept must have expressed the reality of the First Person in a more fitting way. This is the personal name Christ use to express his relation to the First Person of the Trinity and no one has the right to change it.
God's Son is so by nature which means that the eternal interpenetrating love creates a oneness of life, knowledge, will and glory which are equal.
But how are we to understand the seemingly contradictory statement of Christ who said: "My Father is greater than I".(Jn 14:28) We know that in God there is equality of nature and distinction of persons. If the "I" refers to his divine Person, in what sense is the Father greater? This may indicate that the Son is generated by the Father and in that sense subordinate to the Father while remaining fully God. On the other hand, if the "I" refers to the Incarnate Word, then Christ through his humanity is the obedient servant of the Father and in this sense the Father is greater.
Signs of Trinity