I assume that by this statement, '..the actual nature of good at all,...' you meant '...nature of God....'? And thus, His ontological essence.
I would apply a very basic and fundamental approach to this. For such a radical doctrine and concept, and without exception, a paramount one, we would expect a verbose, exhaustive and comprehensive Biblical testimony. Like we do for such paradigm shifts as Faith over Works, and the Gentiles allowance into the Kingdom of God. For the latter two doctrines, we have prophetical attestation, verified by inspired authors, predominantly Matthew. We have didactic passages that explain the grounds for both, the former Law's inception, and the reasons for the subsequent transition to the new Laws. We have explicit passages that affirm and emphasize the Historical results of these changes (Message preached, and Holy Spirit given, to all races, just for believing). And we have all the necessary terminology from the Bible, to define and explain these revelations and doctrines. And we can go on....
None of this can be said about the trinity.
And we can go on...
There are one or two questions I have about the trinity.
How come the Hebrew word for God is a plural?
Why did God say when Adam and Eve ate the fruit, "they have become like us, knowing good and evil". Who is the "us", and who was God speaking to?
When Jesus was baptised, whose was the voice from heaven that said, "This is my beloved Son"? And, what was the bodily form that descended on Jesus from we don't know where?
Is the Holy Spirit, God?
Is Jesus God?
Is the Father God?
How do we explain that?
When Jesus was transfigured, whose was the voice from heaven that said, "This is my beloved Son. Listen to Him."
When Mary met Jesus after His resurrection, why did Jesus tell Mary not to touch Him because He had not yet ascended to the Father?
How come Jesus said that He did only the will of His Father?
Why did John say, "Truly our fellowship is with the Father, and His Son Jesus Christ"?
Why did Paul say, "That I might know you, the only true God, and Jesus whom you have sent?"
If Jesus isn't God, how come He was able to take upon Himself the eternal wrath of God for every single soul who received Christ, past, present and future, within just the three hours He hung on the cross before He died?
How come the Father is a spirit, and no man has ever seen Him, and yet Jesus, as God, is a man that everyone could see clearly?
Who was Jesus crying out to when He said, "My God, my God, why have you abandoned me?" And when He said, "Father, into your hands I commit my spirit".
If the Father is invisible and cannot be seen, who was the fourth person in the fiery furnace with the three young Hebrew men, and was described as someone who looked like "the Son of God?"
And, the Father being invisible, who was the Lord whom Isaiah saw high and lifted up and said, "I am undone"?
Why does the Scripture say that a person who has the Holy Spirit, has Jesus and the Father as well? Does this mean that the Holy Spirit is God as well?
If so, then we have to accept that the Holy Spirit is separate from the Father and Jesus, because Jesus told His disciples that when He goes, He will send the Holy Spirit to be in them, and He will teach them all things they need to know.
I think there is only one way to satisfactorily answer these questions - that God is plural, and is in the persons of the Father, Son and Holy Spirit.
This means that the Scripture is very clear about the trinity, even though it does not use the word, or to define it as such. But it makes is very clear that there are three separate Persons that are identified as God.