"It" is The Key to Growth

So what is something so valuable "it" cannot be priced.
    God gave his son to preach "it."
    And adopted another to teach "it"
"It" is simple but at the same time complex.
One can argue that God devoted the whole Bible to "it."
In short "it" will open your eyes.
But just in case you do not get "it," here is a list of hints: 
    "it" cannot be seen directly,  but is easily known,
    "it" sees everything,
    "it" allows us to see,
    "it" allows us to be free,
    "it" allows us to love,
    "it" gives us understanding,
    "it" involves more than one.
    "it" is essential for a couple,
    "it" is the secret to life.
    "it" is required to see oneself.
    "it" is needed to see the truth.
    "it" is so beautiful we cannot imagine.
    "it" is non judgmental.
Without "it" we are forever lost, confused, never see reality, and will never know love.

So what could be so hidden in plain sight and not be discovered the beginning of time?
Well I'm not telling, because everyone needs to discover this for themselves.

What is it?