Have you ever been called a “know-it-all”? I have, and believe me, it didn’t feel like I had received a compliment. That’s because I hadn’t. When someone calls you a “know-it-all,” they’re sarcastically saying, “You don’t know as much as you think you do!”
But we know somebody who really does know it all: our heavenly Father. God knows everything. His knowledge is immediate, instantaneous, comprehensive, and fully retentive. God knows what He knows without any kind of painstaking research; He never had to go to school, take a test, or be informed about anything. You can never tell God something He doesn’t already know; He knows it all. In short, He is omniscient.
In Psalm 139, David takes the theology of “omniscience” off the top shelf and brings it down to a personal level. To David, God’s omniscience is not theological or philosophical—it’s relational and personal. Notice the personal pronouns here: “Lord, you have searched me and known me. You know my sitting down and my rising up. You understand my thought afar off” (Psa 139:1–2). David doesn’t say, “Lord, you know all things and you’ve searched all things”; instead, he says, “You know me, you’ve searched me” (emphasis mine).
What David does in this psalm is what we must do with all difficult truths we try to comprehend, like “what is the meaning of life?” or “who is God?” We must not be content to leave these questions on a page of a book or discuss them with our friends over coffee. We have to follow David’s lead and find a way to bring them to a personal level.
For example, “You understand my thoughts” (Psa 139:2) could be expressed, “God, you know what I think before I even think it.” What that means to us is this: God knows what we really believe about Him, not just what we say about Him. He knows where we stand, and He knows what our real opinions are.
We Can Never Be Know-It-Alls
When David says “Search me, O God, and know my heart” (Psa 139:23), it’s a prayer. He’s inviting God to know more (even though that’s not possible). He’s saying, “God, I can’t wrap my mind around this. I’ll blow a fuse trying to figure this out, so I just surrender to it. Search me, know me, lead me, direct me.”
And that’s where we ought to leave off in dealing with God’s omniscience and all His divine attributes. I like to put it this way: since God’s ability transcends my reality, it’s best for me to bow at His immensity. God is always greater than our present knowledge of Him. If God were small enough for our brains, He wouldn’t be big enough for our needs.
God indeed “knows it all.” By His very nature, without having to learn anything, He already knows everything—past, present, and future. Faced with that, what else can we do but bow to Him in worship and adoration?
 Barry, J. D., Heiser, M. S., Custis, M., Mangum, D., & Whitehead, M. M. (2012). Faithlife Study Bible. Bellingham, WA: Logos Bible Software.