Coming to the knowledge of God is the purpose of our existence, not merely knowledge
about God, which is the beginning of it all, but direct, intuitive knowledge* of *Him, which is the end. This is also called “seeing” God.
The Church teaches two things about this knowledge 1) man cannot obtain it on his own; it’s completely above our natural ability. Reason can ascertain the existence of God but cannot arrive at the intuitive knowledge of God. That’s a matter of grace, necessitating “the light of glory”, as theologians put it, a supernatural gift from the only one Who can give it. 2) Man, whether in heaven or on earth, cannot know God
comprehensively-presumably we’d have to
be God in order for that to be possible and the distance between us and Him is infinite. IOW, the knowledge is strictly *enabled *by Him, and complete insofar as it fulfills our needs. Faith, itself, is a supernatural foretaste of this knowledge, but it’s fully experienced or consummated, so to speak, in the next life.
184 “Faith is a foretaste of the knowledge that will make us blessed in the life to come” (St. Thomas Aquinas. Comp. theol. 1, 2). CCC
Additionally, according to Aquinas and others, God can grant the experience of His immediate presence-this full knowledge- here and now, at moments, for His purposes, an experience some saints testified about. In any case, this knowledge or vision, even in “dimmer” form, is that which is spoken of in the New Covenant prophecy of Jer 31:
**No longer will they teach their neighbor,
or say to one another, ‘Know the LORD,’
because they will all know me,
from the least of them to the greatest,”
declares the LORD. **Jer 31:34
For now we see in a mirror dimly, but then face to face; now I know in part, but then I will know fully just as I also have been fully known. 1 Cor 13:12
Again, this knowledge is not a natural knowledge-which is probably what most of the sources you referenced are speaking of. It’s an “intellectual vision” that depends on grace-man cannot attain to it on his own. It begins with faith:
"All things have been committed to me by my Father. No one knows the Son except the Father, and no one knows the Father except the Son and those to whom the Son chooses to reveal him." Matt 11:27
Let me re-emphasize; without grace, man’s knowledge of God is only “head-knowledge”, allegorical at best. And a believer’s experience here on earth may well remain much that way-depending.
More from the Catechism:
**35 Man’s faculties make him capable of coming to a knowledge of the existence of a personal God. But for man to be able to enter into real intimacy with him, God willed both to reveal himself to man and to give him the grace of being able to welcome this revelation in faith. The proofs of God’s existence, however, can predispose one to faith and help one to see that faith is not opposed to reason.
52 God, who “dwells in unapproachable light”, wants to communicate his own divine life to the men he freely created, in order to adopt them as his sons in his only-begotten Son.3 By revealing himself God wishes to make them capable of responding to him, and of knowing him and of loving him far beyond their own natural capacity.
53 The divine plan of Revelation is realized simultaneously "by deeds and words which are intrinsically bound up with each other"4 and shed light on each another. It involves a specific divine pedagogy: God communicates himself to man gradually. He prepares him to welcome by stages the supernatural Revelation that is to culminate in the person and mission of the incarnate Word, Jesus Christ.
St. Irenaeus of Lyons repeatedly speaks of this divine pedagogy using the image of God and man becoming accustomed to one another: The Word of God dwelt in man and became the Son of man in order to accustom man to perceive God and to accustom God to dwell in man, according to the Father’s pleasure.
163 Faith makes us taste in advance the light of the beatific vision, the goal of our journey here below. Then we shall see God “face to face”, “as he is”. So faith is already the beginning of eternal life:
When we contemplate the blessings of faith even now, as if gazing at a reflection in a mirror, it is as if we already possessed the wonderful things which our faith assures us we shall one day enjoy.
1028 Because of his transcendence, God cannot be seen as he is, unless he himself opens up his mystery to man’s immediate contemplation and gives him the capacity for it. The Church calls this contemplation of God in his heavenly glory “the beatific vision”:
How great will your glory and happiness be, to be allowed to see God, to be honored with sharing the joy of salvation and eternal light with Christ your Lord and God, . . . to delight in the joy of immortality in the Kingdom of heaven with the righteous and God’s friends. **
CATECHISM OF THE CATHOLIC CHURCH