I have heard that quote from Saint Patrick before. McMullan is Irish, ya know! But frankly, it’s exactly the sort of thing that doesn’t help. And St. Patrick might just as well be explaining the Mormon Trinity. I really need to understand it in terms of the Redemption of Man and for that to work, I need to know who Jesus was praying to in the garden of Gethsemane.
Why did Jesus pray? First, He wanted to show us what to do and how. Jesus didn’t need to be baptized by John, either, but He did it to show us the way, and He explained it to John the Baptist: “Let it be so now; for thus it is fitting for us to fulfil all righteousness” (Mt 3:15). Second, in becoming fully human from the time He was born until the time He died on the cross, Jesus voluntarily took on human limitations. He hungered, thirsted, and needed parents to provide for Him. One of those limitations is a lack of mental telepathy. Jesus maintained constant communication with the Father in the human way: prayer. After His resurrection, when Jesus has once again embraced His abilities as God, the bible makes no mention of Jesus praying.
In trying to describe the difference in our perspective and God’s perspective, I sometimes talk about creatures which dwell underwater. I can swim with them and experience life as they know it. But to communicate with those on the surface, I must use a different way than I am accustomed to using above the water. And while I am underwater I do not forget what life on a mountaintop is like; that knowledge stays with me, just as Jesus kept his knowledge of being God. However if I were trying to explain life on a mountaintop to an intelligent-enough dolphin, I would be unable to fully do so because the dolphin has no frame of reference to understand. How do you explain “dry” to a sea-creature? To them “dry” is also “dead.” I could give the dolphin a general idea, little more. In the same way, we will not fully understand the nature of our triune God until we actually join Him in heaven.
One way to try to grasp the concept of the Trinity is to look at an egg. It has three component parts - shell, yolk, and white. In order to be an egg, it must have those three parts. While all 3 parts are “egg”, and can be used separately, they are best and most meaningful when together. (Yes, an egg has other parts, too, but they are all sub-components of shell, yolk, and white.) Eliminate one of the three and it is missing a necessary element. The part we see revealed to the world is the shell, which we can compare to Jesus - God presented to us in a way we can touch. The part hidden from us is the yolk which we can compare to God the Father, the procreative portion and origin of new life, dimly visible through the shell. The part inbetween, nearly invisible in to the eye, is the white, which can be compared to the Holy Spirit - we may not see it right away, but when the egg is opened we can easily feel it and observe its effects.
One of the points of the egg analogy is to illustrate the interdependence of our triune God. Jesus is fully God, but not all by His lonesome. Same with the Father and the Spirit. You can even ignore one or two of the three, just as you can imagine that the eggshell has no contents worth examining, or look only at the yolk and ignore the rest. The Father is still God, even to Jews and Muslims who don’t believe in Jesus, and vice-versa. But you have an incomplete picture unless you acknowledge all three together.
In the Book of Revelation we see Jesus standing beside the Father. How can this be if they are both one God? It is like the eggshell, the egg white, and the egg yolk being beside each other. Each component is still “egg”, not peas and carrots or anything else. Together they are the complete egg. Together, the Father, Son, and Spirit are the complete God.
In the final analysis, Trinity will not be completely comprehensible to us until we enter heaven to behold Almighty God as He is, rather than as through a glass, darkly, the way we do now.