More from "Heaven Sense" (page 3-4)
Heaven is essentially the sight of God face-to-face.
Almost eighteen hundred years ago St. Irenaeus wrote:
The things that are impossible with men are possible with God. For man indeed of himself does not see God. But God of His own will is seen by those whom He wills, when He wills, and as He wills. For God is mighty in all. He was seen then [by the Prophets in the Old Testament] through the Spirit of prophecy; He is now seen in the New Covenant, by adoption also, through the Son; but in the kingdom of Heaven, He will be seen even as Father. Man will be prepared by the Spirit in the Son of God. Man will be brought to the Father by the Son; man will be endowed with incorruption by the Father unto everlasting life, which comes to everyone by the fact of his seeing God. For as those who see the light are in the light and perceive its brightness; thus also those who see God are in God, perceiving His brightness. This brightness gives them their life; hence, they who see God, see life. God is beyond created grasp, intelligence, and sight, but He will put Himself within human sight, intelligence, and grasp for the purpose of giving life to those who perceive and see Him. God's greatness is indeed unsearchable, but so also is His loving kindness unutterable, even that loving kindness by which, being seen, He gives life to those who see Him.
footnote St. Ireneaus (c. 125-c. 203; student of St. Polycarp, missionary, bishop of Lyons, and Church Father).
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Another note about St. Ireneaus; notice that he was the student of St. Polycarp. St. Polycarp was the student of St. John the Apostle, one of the twelve chosen by Jesus. So St. Ireneaus learned about Jesus directly from someone personally taught by Jesus' Beloved Apostle, St. John the Evangelist.
So this profound and accurate perception that speculates (accurately) about the nature of heaven was written by someone who was a "grandchild" level disciple from when Jesus lived.
What St. Ireneaus describes is that heaven and all of existence within it exists because God can be seen. It is living within the light of God's existence and being able to perceive Him that grants eternal life. You could think of it as the sight of God in heaven is the atmosphere that allows each eternal soul to live. So people in heaven not only are "able" to see God they must see God, because it is the sight of God that provides the eternal life of the soul through His light.
Understanding this about heaven helps understand its opposite, which is hell. The souls in hell are not being punished by not being able to see God; hell exists because it is the place where God is not seen or perceived at all. This does not mean that hell is outside of God's control, to the contrary, it is the place prepared by God for the damned through his withdrawing of His light from that place. It is the sight and light of God, as St. Ireaneaus explains, that maintains the life of each eternal soul in heaven. This maintenance of eternal life and blissful rest is withheld from hell.