Fair enough,but Im not much of a teacher.
First thing up to bat is Platonic dualism. The universe is divided up into what is in motion and what is at rest. Previously Heraclites popularized everything in flux but Plato popularizes only what we can sense is in flux but what we perceive by the intellect is constant. Picking up his thinking on the constant side probably from Parmenides; who emphasized oneness and constancy.
From Plato: The seen is the changing, and the unseen is the unchanging. Phaedo
From Paul: 2 Cor 4:18 As we look not to the things that are seen but to the things that are unseen. For the things that are seen are transient, but the things that are unseen are eternal.
Materialism verses idealism is the major philosophical debate with Christianity falling on the side of Plato and the idealists. Being initiated at this time is recognizing the spiritual side of the universe.
SOCRATES: Take a look round, then, and see that none of the uninitiated are listening. Now by the uninitiated I mean the people who believe in nothing but what they can grasp in their hands, and who will not allow that action or generation or anything invisible can have real existence. Theaetetus
Now the big thing to understand here is that Platos spiritual side of the universe isnt understood as it was commonly understood at the time. The understanding of the spiritual elements at the time doesnt come from philosophers but poets, specifically Homer. These gods are understood like how they are presented in the poems which is like people. Platos constant understanding of the spiritual elements opposes this thinking and also any incentive to sacrifice to them. This is why Socrates and early Christians get accused of being atheists because compared to how they had historically been understood, they werent any type of god at all. To the platonic philosophers, the spiritual side isnt engaged by sacrifices and ritual but by the intellect.
That which is apprehended by intelligence and reason is always in the same state; but that which is conceived by opinion with the help of sensation and without reason, is always in a process of becoming and perishing and never really is. Plato Timaeus
The intellect shows an ideal concept, while sensation shows a flawed particular of that concept. This is seen in simple forms like a circle being perfect in concept but a particular of a perfect circle in the material world would be impossible to achieve. A person also can be a particular of a spiritual element and this is where you get stuff like Jesus being the Word in the flesh. The Word there is actually Logos which means Reason in Greek. This is because Jesus is seen as embodying it perfectly with is life and death.
Reason (Logos), to the idealists, is a real spiritual element that can be personified by a person, which Jesus is said to have done. This spiritual elements are thought to have been created from an initial spiritual element that gets labeled God or the Father. The big thing to understand about Platos understanding of God is that it is unknowable.
the father and maker of all this universe is past finding out; and even if we found him, to tell of him to all men would be impossible. Timaeus
Because to the idealists every idea you have in your head is a created entity, none of them can be the creator. While we can conceive of the spiritual side we cant conceive of its creator because we are working with things that are different than the creator of those things. This is why you have Paul pointing at the unknown god in Acts.
Now Platos and the early church fathers understanding of God wasnt only unknowable but it was actively creating. Because the main belief is that the spiritual elements were constant, whatever God was doing at the beginning, God is still doing now.
This is in contrast with something more materialistic like Aristotle put forward, where there may be a creator but after the creation, the clockwork nature of the universe doesnt require an active God. Because Plato saw matter as being formed by the ideals and the God as the constant creator of the ideals he required an understanding of God that was still active
So now you have a man who is personifying a spiritual element, that is being actively manifested by the activity of another spiritual element. Son, Ghost and Father.