Omniscience
Omniscience means God knows everything. The word comes from two Latin words: omnis, “all,” and scientia, “knowledge.” The word itself is not in the King James Bible, but the idea is on almost every page.
What the Bible Says
God knows every fact about the world He made. “Neither is there any creature that is not manifest in his sight: but all things are naked and opened unto the eyes of him with whom we have to do” (Hebrews 4:13). He knows when a sparrow falls, and He knows the number of hairs on your head (Matthew 10:29–30).
He knows what people think, not just what they do. In Acts 1:24 the disciples pray to the Lord, “which knowest the hearts of all men.” The Greek word there is καρδιογνώστης (kardiognōstēs), “heart-knower.” David wrote that God knew his words before he spoke them (Psalm 139:4).
He knows the future. He is the God “declaring the end from the beginning, and from ancient times the things that are not yet done” (Isaiah 46:10). In Isaiah, knowing the future is the very thing that sets the true God apart from idols (Isaiah 41:22–23).
He even knows what would have happened. David asked God whether the men of Keilah would hand him over to Saul. God said they would, so David left, and it never happened (1 Samuel 23:10–13).
God Does Not Learn
People gain knowledge. We learn, we figure things out, and we forget. God does none of these. “Who hath directed the Spirit of the LORD, or being his counsellor hath taught him?” (Isaiah 40:13). Nothing has ever taken Him by surprise.
So what about verses where God seems to find something out? After Abraham raised the knife, God said, “now I know that thou fearest God” (Genesis 22:12). Other verses say the LORD “repented,” meaning He was sorry (Genesis 6:6).
1 Samuel 15 helps here. Twice the chapter says the LORD repented that He had made Saul king (verses 11 and 35). In between, Samuel says God “will not lie nor repent: for he is not a man, that he should repent” (verse 29). The same writer uses the word both ways in the same chapter, and he was not confused. He was describing God’s real grief in words people understand. He was also making clear that God never changes His mind the way a man does when something catches him off guard.
A few teachers today read Genesis 22:12 to mean God truly did not know until that moment. Part 2 looks at that view.
“Neither the Son”
Jesus said of the day of His return, “of that day and that hour knoweth no man, no, not the angels which are in heaven, neither the Son, but the Father” (Mark 13:32). How could the Son of God not know something?
Christians since the early church have answered this the same way. Jesus is fully God and fully man. As God, He knows all things. As a man, He had a real human mind that grew and learned; Luke says He “increased in wisdom” (Luke 2:52). Athanasius, a bishop in Egypt in the 300s, explained that not knowing the day belonged to Christ’s human nature, not His divine nature. Jesus was speaking as a man.
Why It Is Hard to Picture
When we try to imagine knowing everything, we picture someone with a very large memory. That picture is far too small. Our knowledge comes in pieces, one moment at a time, and God’s knowledge does not. He is not standing at one point in time looking ahead. He sees all of history at once, the way a man on a mountaintop sees the whole road below him.
Most confusion about omniscience comes from putting our own limits on God and then wondering how He gets around them. The biggest of these questions is this one: if God already knows what I will choose tomorrow, am I really free to choose? That question is the subject of Part 2, Foreknowledge.