1:4 chosen us. God chose us by His own will (Ephesians 1:11), not because He could foresee our choice of Him. Jesus made this compellingly clear: “Ye have not chosen me, but I have chosen you” (John 15:16). Nevertheless, from our human perspective, every believer has also made his own willing decision to receive Christ (John 1:12; 3:16; Romans 10:13; etc.).
1:4 foundation of the world. God in Christ was the Creator of the space/matter/time universe, but before He began the world, in some way beyond our comprehension, we were chosen in Him. Note also the other events that were planned, and (since God does not change) in effect all consummated before the world began: (1) love within the Godhead (John 17:5,24); (2) Lamb of God slain (I Peter 1:20); (3) names written in Book of Life (Revelation 13:8; 17:8); (4) chosen ones saved by grace (II Timothy 1:9); (5) saved ones given assurance of eternal life (Titus 1:2); (6) established hidden wisdom of God (I Corinthians 2:7); (7) all God’s works known and planned (Acts 15:18). Even though our finite minds cannot really comprehend such truths, we can believe them since God has revealed them to us. He did not say we must understand the full depths of His gospel to be saved; we just have to believe!