What does it mean that God is omniscient?
The word "omniscient" simply means all-knowing: God knows everything, everywhere, in every direction of time. The Bible presses two questions on us — how far does that knowledge reach, and what does it feel like to be the person He knows that completely?
Knowledge without limits
Commentators describe God's knowledge the way they describe His power: infinite, with no edge to it. It covers space and every part of time, and it extends to the smallest details of creation.
James McBroomLike His wealth and wisdom, this is infinite. He both knows and foreknows; He is both Prescient and Omniscient. His knowledge is linked with His Omnipresence as related to the dimensions of space — above, beneath, around — and with the three variants of time: past, present, and future. This also links with His Omnipotence, for to know what will take place at a future time means that all is under His control. He tells the number of the stars and numbers the hairs of our heads.
That link between knowing and ruling matters. If God can announce what has not happened yet, then the future is not a guess to Him.
James McBroomThere is a close link between omniscience and omnipotence, for, to take in all the ages and foretell what will come to pass in dim and distant times, God must have the hearts of all men under His direct control. Known to God are all His ways from the beginning, and as we trace these ways, and see how He makes both sin and Satan serve Him, we can understand how He works out His purposes of eternity in connection with the failure of the creature.
Knowledge that reaches inside people
Human knowledge stops at the surface. God's does not, and Scripture treats that as something no one else can claim.
Arend RemmersHe is omniscient, all-knowing. He is the only Being able to do so. Solomon says in 1 Kings 8:39, "for you, you only, know the hearts of all the children of mankind." This can only be said of God. He knows the inward thoughts and feelings of every man.
Already searched, not being searched
Psalm 139 does not say God is in the process of finding us out. The verbs are finished. Our whole story is already read.
J. N. DarbyEvery human being has been searched by Omniscience, whether he is conscious of it or not. This will be made clear "in the day when God will judge the secrets of men." ... He has "hemmed us in, behind and before." He can look backward, and He can look forward also. All our history is before Him, as if it had been written after we had run our course. "O LORD, you have searched me" is the language of the Psalmist — not "you are doing it now, or will do it later," but you have done it already.
Why this is the ground of peace, not panic
The same writers who call this searching solemn also call it the foundation of rest. The reason is that God's offer of forgiveness was made with full knowledge of what He was forgiving.
The Christian's FriendWe must recognise then that God knows us, knows us just as we are, knew us from the very outset... God knows us from the beginning to the end of our course. But then the same God has spoken to us in the gospel of the forgiveness of sin. And it is forgiveness of sin according to His omniscience, therefore of all sin; and if God speaks to us of the righteousness of faith, it is, according to His omniscience, "everlasting righteousness."
The same article locates the usual obstacle to peace in ourselves: waiting to discover we are better than God already knows us to be, instead of resting in the fact that "God acts upon His own omniscience as to what we are, and not upon what we are thinking of ourselves."
From distress to comfort
Psalm 139 itself moves. The believer's first reaction to being fully known is not joy — it becomes joy.
Hamilton SmithIn the experience of the psalmist the consciousness of the omniscience of God at first plunges his soul into the deepest distress as he thinks of his own broken responsibilities towards God. When at last he realises that God's "works" and God's "thoughts" are toward him in grace, the omniscience of God becomes the source of his deepest comfort.
Writing on Ruth, the same author puts the point in one line: nothing so wins and comforts the heart as learning, in the Lord's presence, that "He that knows all, and yet He loves me."
Seen in Jesus
The attribute is not left in the abstract. Commentators point to it working in a Man who walked among us.
H. H. SnellIs omniscience an attribute of God? We read that "He knew all people and needed no one to bear witness about man, for He Himself knew what was in man." He knew the people's thoughts. He knew that the Father had given all things into His hands, and knew all that would come upon Him... On one occasion His disciples cried out, "Now we know that you know all things"; and after His resurrection Peter said, "Lord, you know everything."
Summary
- Infinite. God's knowledge has no boundary in space or time; He both knows and foreknows, down to the stars and the hairs of your head.
- Inward. He alone reads hearts — thoughts, motives, and words before they are spoken.
- Already. You have not been put under examination; you have been searched, past and future together, as if your whole life were already written.
- Grace. Because He knew the worst first, His forgiveness covers all sin and His righteousness is everlasting — nothing later can surface and undo it.
- Comfort. What first crushes the soul ends as its deepest rest: the One who knows everything about me loves me still.