The Son and the Father are known only to each other, which is another way of saying that what a mind truly is cannot be found by looking outward or reasoning inward. The ego builds its guesses about identity from the body and the world, but none of them touch the reality, for that is held between the Source and what it created, in a knowing the separate self has no access to.
Yet the knowing is not sealed away. It reveals itself to whoever the awakened mind draws in, passed from one to another as sight is passed to the newly seeing. The meaning rests here: a mind does not deduce who it is; it is shown, and it is shown by the very love it had forgotten was its own.
Father: the Source of the mind, the love that creates and knows.
Son: what the mind truly is, the created self held in the Father's knowing.
Man: the mind that looks from separation and so cannot find by searching what only love reveals.