If God is the One of whom there is none greater, then He must be all-knowing (omniscient), meaning that He has complete, knowledge that is beyond measure (Ps. 147:4-5). If anyone knows something He does not know, then His knowledge is not perfect.
An All-Knowing God Knows the Big Picture
An omniscient God knows what has happened, what will happen, and what is happening now. He knows the beginning and the end, hence the big picture. To be God, He must know how all the pieces fit together. Otherwise, He is just one of the many pieces — a part of, not above and beyond. Consequently He would not have sovereign rights.
An Omniscient God Knows What Will Happen Before It Occurs
Knowing the future is part of what sets the God of the Bible apart from other gods (Isa. 41:22-24; 44:6-8). Anyone can learn from history. To know what will happen, with total accuracy, before it occurs, can only be attributed to the true God. — “I am the LORD; that is my name! I will not yield my glory to another or my praise to idols. See, the former things have taken place, and new things I declare; before they spring into being I announce them to you.” (Isa. 42:8-9)
Implication: While there are a lot of things we don’t understand about the foreknowledge of God, one thing we can be sure of is that it enables Him to work all things out for the good (Rom. 8:28-32; Jer. 29:11). This is a God we can trust to be for us now and through all eternity.
A God Who Knows All is Self-Sufficient
Someone who knows all there is to know doesn’t need counsel or instruction (Isa. 40:14). Romans 11:34 describes God as the One with such a reservoir of wisdom and knowledge that no one comes close to being His equal. Consequently, He is sufficient unto Himself, a prerequisite for being God. His ways and thoughts are so much higher than ours (Isa. 55:9) that there isn’t anything we could tell Him that would improve His plans.
Implication: We can gain perspective in the realization that God doesn’t need our help in determining the right course of action. Who are we to tell Him what He should or shouldn’t do? Think about Job’s questions about the justice of his suffering. God responded by contrasting His power and knowledge with limited human knowledge (Job 38-41). To all of this, Job could only confess, “Surely I spoke of things I did not understand, things too wonderful for me to know” (Job. 42:1-3).
To Be All-Knowing God Must Know Even the Secrets of the Heart
God not only knows our observable behavior but also what is invisible, deep within that no one else can see or fully understand. He knows what we will say even before we open our mouths (1 Chron. 28:9; Ps. 139:4; Matt. 6:8). Though we may fool others, He knows our guilt and innocence, whether we have a faithful or idolatrous heart (Ps. 44:21; 69:5; 1 Jn. 3:19-20).
Implication: Since there is no place we can hide from God and nothing we can hide from Him (Ps. 139:1-12), why not work in cooperation with God rather than fight against Him (Ps. 139:23)? — Nothing in all creation is hidden from God’s sight. Everything is uncovered and laid bare before the eyes of him to whom we must give account. (Heb. 4:13)