Ephesians 1 is another favourite passage of the illiterate Calvinist where they focus too much attention on the first twelve verses. The very first verse tells us that Paul's audience was "the faithful in Christ Jesus." The "in Christ" theme introduced in the opening sentence continues through this entire section of the text, repeated ten times in thirteen verses. The Calvinist contends that pre-selected individuals were chosen before the foundations of the world and predestined to become believers. However, that is not what the text says.
Does Paul ever actually say that certain individuals were predestined to believe in Christ?
Does Paul ever actually state that God chose particular individuals to be effectually placed in Christ?
Does Paul ever actually state that Christ redeems individuals so they might irresistibly be placed in Him?
Of course not! So what does the text say? Paul speaks of what "the faithful in Christ" (v.1) have been predestined to become—not about God pre-selecting certain individuals before the foundations of the world to be irresistibly transformed into believers. Paul teaches that those "in Him" have been predestined to become "holy and blameless" (v.4) and "to be adopted as sons" (v.5). Paul is speaking of what the believer is chosen to become. "He predestined us ["the faithful in Christ" (v.1)] for adoption to sonship through Jesus Christ" (v.5). In other words, whoever believes in Him is predestined to become "holy and blameless in His sight" (v.4), which parallels Paul's teaching in Romans 8:29, which states, "He also predestined ["those who love God" (v.28)] to become conformed to the image of His Son."
"Just as" (v.4) means "to an equal degree; in the same way; at the same time." To an equal degree, in the same way, and at the same time, what is said in verses 3, 4, and 5 are all true. They are conditioned upon being "in Christ." This is what was determined for those who are and remain "in Him."
According to Paul, believers "wait eagerly for our adoption as sons, the redemption of our bodies" (Rom. 8:23), because that is what believers have been predestined to become, provided we abide in Christ. If we continually remind ourselves that the "us" being referenced through this chapter are "the faithful in Christ" (v.1), then the apostle's intention, and the context, becomes quite clear. Before the foundations of the world, God has predestined us, the faithful in Christ, to become holy and to be adopted. That is all the text says! Anything else is being imposed upon it through eisegesis.
Believers are not fully adopted until they take up residence in the home of the one who has adopted them. This is where most professing Christians confuse the future with the present in their bankrupt theologies. Until such a point, believers look forward with great anticipation to their adoption (as seen from Romans 8:23).
When Paul speaks of "we" and "us" in the first 10 verses, he includes all Christian believers. Verses 11-12 apply to the people of Israel, whom Paul identifies himself with, being a Jew. This is in distinction from the "Gentile" believers ("you also") to whom he speaks of in verse 13. Calvinists should pay attention to this verse in particular: "In Him, you also, after listening to the message of truth, the gospel of your salvation." Were individuals included in Christ before the foundation of the Earth? No! Paul said it was "after listening to the message of truth."
Paul continues, "having also believed, you were marked in Him." Were individuals marked in Him before the world began and without regard to their response to the Gospel? No! Paul states clearly that they were marked "in Him" when they believed the message of truth.
Ephesians chapter 1 is not about God predetermining which individuals will be in Christ; this passage is about God predetermining the spiritual blessings for those who are in Christ through believing the word of truth (vv.1-3). Romans 8:29 says that God "also predestined ["those who love God"] to become conformed to the image of His Son." It says nothing about predetermining who will believe! Calvinists need to learn how to read. If they did, they would not be embracing and teaching the heresy that was first taught by the Gnostics and rejected by the early Christians (A.D. 90-300).