The main division in the word of God is between prophecy concerning Israel and her kingdom (spoken by the prophets since the world began, Acts 3:21) and the mystery of the Body of Christ (kept secret since the world began, Rom. 16:25). This main division reveals the twofold purpose of God.
Perhaps a better way to say it is that God has one great purpose that will be fulfilled through a twofold plan for the ages. God’s one great purpose is to be glorified through the Lord Jesus Christ. The twofold plan through which He will accomplish this is implied in the very first verse of the Bible. God will be glorified in heaven and earth (Gen. 1:1). As the most high God, the Lord is the possessor of heaven and earth (Gen. 14:19, 22). There has been a rebellion in both, but Christ will reconcile all things in heaven and earth back to God (Matt. 28:18). The twofold plan concerns how God will reconcile the governments of both heaven and earth back to Himself (Col. 1:16-20). Israel is His vehicle to reconcile the government on the earth. The Body of Christ is His vehicle to reconcile the government in heavenly places.
From Gen. 1 until Paul’s ministry, God’s revelation concerned His plan for the earth. One of the spiritual blessings we have as members of the Body of Christ is that God has made known to us the mystery of His will concerning heaven (Eph. 1:8-12, note the words "purposed" v.9 and "purpose" v.11). The mystery of the Body of Christ was no afterthought or plan B! It was His "eternal purpose" that He kept hid in Himself until He revealed it through Paul (Eph. 3:11). It is a demonstration of His great wisdom (Eph. 1:8; 3:10; 1 Cor. 2:7).
Anti-dispensational preachers accuse us of teaching that God failed in trying to establish His kingdom through Israel. They claim Christ came to establish a spiritual kingdom and that His promises to Israel are fulfilled spiritually in the church. Those that spiritualize the plain words of scripture tell spiritual lies. Israel failed, not God! He knew they would fall, and He planned that through their fall He would reconcile the world to Himself (Rom. 11:11-15, 32-36).
Some think the dispensation of the fulness of times (Eph. 1:10) refers to the kingdom age. I believe it is the eternal state after the creation of a new heaven and earth when the full purpose of what God revealed in time finally comes to fruition. Verse 10 summarizes the goal of God’s twofold purpose. Christ is central in all that God is doing. There is one family of God (Eph. 3:14-15), but there will be a distinction throughout eternity between the things in heaven and earth. Notice that the things in heaven and earth will all be gathered together "in Christ." All the redeemed are in Christ. A person can only be “in Adam” or “in Christ” (1 Cor. 15:22). Christ is the foundation and center of both programs (“chief corner stone” Eph. 2:20; 1 Pet. 2:6). So, the fact people were in Christ before Paul (Rom. 16:7) does not prove the Body of Christ began before his ministry. What makes the Body of Christ distinct is that it is neither Jew nor Gentile, but one new man.
1) God’s purpose for heaven concerns the church which is the Body of Christ. We are His heavenly people (Phil. 3:20; Eph. 2:6; Col. 3:1-4). The Body was planned BEFORE foundation of the world (Eph. 1:4) but kept secret since the world began until it was revealed through the apostle Paul (Rom. 16:25). To understand this program, we must study Paul’s epistles because that is where it is revealed (2 Tim. 1:8-13). We have been predestinated to be glorified with Christ and reign with Him eternally in the heavens (2 Cor. 5:1).
2) God’s purpose for the earth concerns the nation of Israel (Isa. 14:24-27). By Gen. 11 (the first 11 chapters cover 2,500 years), God gave up on the Gentile world (Rom. 1:18-32) and chose Abraham. He made an everlasting covenant to make of him a great nation and to give him and his seed a special land (Gen. 12). Israel is to be a light to the other nations. God also made an everlasting covenant with David concerning his throne and kingdom (2 Sam. 7). Christ will reign on the earth from the throne of David in Jerusalem over the whole world (Ex. 19:5-6; Jer. 23:5-6). This was prophesied FROM foundation of world (Matt. 25:34); it was spoken by the prophets since the world began. The rest of scripture concerns this program. Israel will reign with Christ on earth over the nations.
In keeping the Body of Christ a secret, God was especially keeping it a secret from Satan (1 Cor. 2:6-8). God ordained it "before the world" (v.7), but kept it secret from the "princes of this world." The rebellion against God's government began before He created Adam (and I personally believe that the creation of man was in response to that challenge and rebellion, Ps. 8:2). Satan and the angels that followed him operate primarily in heaven (Eph. 2:2; 6:12; Rev. 12:8). The heavens are not clean in God's sight (Job 15:15). That is why God did not say the firmament of heaven was good (Gen. 1:8). When God created Adam, He commissioned him to "subdue" the earth (Gen. 1:28) which basically means to conquer. He said that before the fall, so we know that He was not referring subduing wild plants and animals. There must have been enemies already in existence.
From Genesis 1 (v.2) up until the ministry of Paul, God's revelation concerned His purpose for reconciling the earth, and so that was Satan's focus. Satan usurped Adam’s dominion on the earth and became both the prince and god of this world. In having Christ crucified, Satan thought that he had defeated or at least hindered that purpose. What he didn't know was that "by the cross" (Eph. 2:16) God would form a new group of believers with the purpose of giving us the high privilege of reigning with Him in the heavenly places. We will replace Satan and his angels when they are finally cast out of heaven. This was His purpose ever since the rebellion of Lucifer that took place BEFORE the foundation of the world, but He had to keep it a secret until Satan deceived himself by crucifying Christ.