The attribute of God by which He knows all things — perfectly, simultaneously, and eternally — without learning, discovery, or limitation. God's knowledge is not acquired; it is self-originating and infinite. He knows every heart (1 Kings 8:39), every word before it is spoken (Psalm 139:4), every deed done in secret (Hebrews 4:13), and the end from the beginning (Isaiah 46:10). His omniscience grounds His perfect justice (He cannot be deceived), His trustworthy prophecy (He declares what He knows will be), and the Christian's comfort (He knows your situation completely and acts with full knowledge).
OMNIS'CIENCE, n. The quality of knowing all things; infinite knowledge; an attribute of God only. The omniscience of God is the foundation of all religious trust — for a god who does not know cannot reliably help, judge, or save.
Open theism — a theological movement that gained academic traction in the late 20th century — argues that God does not know future free choices, thereby "limiting" His omniscience to make room for human freedom. This redefines God in man's image: a very capable, well-meaning being who is learning along with us. Scripture rejects this flatly (Isaiah 46:9–10; Acts 15:18). The comfort of omniscience is also eroded by a surveillance-age culture that frames being "known completely" as threatening rather than as the foundation of trust and love.
Psalm 139:1–4 — "O LORD, You have searched me and known me... You understand my thought from afar... and are intimately acquainted with all my ways."
Isaiah 46:10 — "Declaring the end from the beginning, and from ancient times things not yet done."
Hebrews 4:13 — "No creature is hidden from His sight, but all are naked and exposed to the eyes of Him to whom we must give account."
1 John 3:20 — "God is greater than our heart, and He knows everything."
Matthew 10:30 — "But even the hairs of your head are all numbered."
H3045 — yada (יָדַע): to know, perceive, be acquainted with — the primary Hebrew word for God's knowing
G1097 — ginōskō (γινώσκω): to know, perceive, understand — often used of God's intimate knowledge
G4267 — proginōskō (προγινώσκω): to foreknow — God's knowledge of events before they occur (Rom. 8:29)
Because God is omniscient, prayer is not informing Him of facts He lacks — it is communion with One who already knows, and an act of submission to His perfect understanding of our situation.
God's omniscience makes His promises absolutely reliable: He does not promise based on what He hopes will happen, but on what He knows will come to pass.
For the believer, omniscience is not a threat but a comfort — to be fully known and still fully loved is the deepest possible assurance.