Eph 1:4 just as He chose us in Him before the foundation of the world, that we should be holy and without blame before Him in love,
The purpose for which we were chosen in Him was to set us apart (holiness), to be made uncommon. Various believers approach this verse, and the one that follows, from different angles. Here is my understanding of it: God’s original plan for human creation was that we would be holy and blameless (perfect). When Adam sinned God’s original plan was not done away with, He fulfilled them in Christ.
The last Adam, Jesus the Restorer, was ordained for us from everlasting so that no life, especially that of Christians, would exist apart from Him. This verse in my judgment fortifies verse 3 to indicate that God did not have a plan B after the fall of man. He had plans for man’s redemption even before the creation of the world. This is the hope of our calling, the blessed hope. We were not an afterthought but part of His divine plan.
How then are we lawbreakers chosen in Him? I cite Paris Reidhead, “The lawgiver was the law keeper that He May justify the lawbreakers.” That is, “All that God has commanded in the law is all that He has provided in the gospel” (Michael Horton). This was God’s plan to save His chosen. Joh 15:16, “You did not choose Me, but I chose you and appointed you that you should go and bear fruit, and that your fruit should remain, that whatever you ask the Father in My name He may give you.”