Our knowledge is partial, ectypal, composite, and learned, but God’s is complete, archetypal, simple, and innate. Hence, God is omniscient, that is, all-knowing (1 Samuel 23.10-13; 2 Kings 13.19; Psalm 139.1-6; Isaiah 40.12-14; 42.9; Jeremiah 1.4; 38.17-20; Ezekiel 3.6; Matthew 11.21). God depends on the world no more for His knowledge than for His being. Nor can His knowledge be any more circumscribed than His presence or duration. Even when we foreknow things hidden from others, our knowledge is finite and fallible. However, God’s foreknowledge is qualitatively distinct. For us, knowing certain things is accidental to our nature. Our humanity is not threatened by our ignorance of many things. However, God’s simplicity entails that none of His attributes are added to His existence. It is impossible for God not to know everything comprehensively. Given His eternality, He knows the end from the beginning in one simultaneous act. God knows all things because He has decreed the end from the beginning and “works all things according to the counsel of His will” (Ephesians 1.11). This knowledge is inseparable from God’s wisdom (Romans 8.28; 11.33; 14.7-8; 1 Corinthians 2.7; Ephesians 1.11-12; 3.10; Colossians 1.16).
In Scripture, God’s knowledge and wisdom are closely related to veracity or truth… God is truth – in an ethical sense (i.e., fidelity: Numbers 23.19; John 14.6; Romans 3.4; Hebrews 6.18) and in a logical sense (i.e., knowing how things really are). These characteristics converge in the prominent biblical theme of God’s faithfulness…which is defined by His commitment to His covenant. It is this faithfulness that is on trial in covenantal history, involving Israel and Yahweh in the interchanging roles of judge, defendant, and witness – with testimony and counter-testimony mediated by the prophets.
God’s simplicity also cautions us against raising God’s omnipotence above His other attributes. God always exercises His power in wisdom, knowledge, and truth. In fact, God is not able to exercise His power in a manner that is inconsistent with any of His other attributes.
From: The Christian Faith: A Systematic Theology for Pilgrims on the Way by Michael Horton (Grand Rapids: Zondervan, 2011), pp. 259-260.