Dispensational Bible Truth takes note of God’s eternal purpose of the ages that include several changes in salvation requirements that He has introduced… since Creation. These Biblical ages may be distinguished as different Dispensations or administrations of God during the several Biblical ages… from the creation of Adam to eternity. These Dispensations are named or titled as follows, with their brief descriptions. 

• INNOCENCE - Created in innocence with free will, Adam fell to “Sin” issuing in bondage, sin and death coming upon the whole human race being in the lineage of Adam (cf. Rom. 5:12).
• CONSCIENCE - Adam and Eve were driven from the Garden, having eaten of the “Tree of the Knowledge of Good and Evil.” Thereby man was required to live by his ‘conscience.’ This ended with man being “continually evil” and being judged with Noah’s flood, saving 8 souls in the Ark.
• HUMAN GOVERNMENT – Then the repopulated earth resulted in mankind congregating… contrary to God’s instruction to replenish the earth. They desired to reach heaven on their own, building the Tower of Babel. Then God confounded their languages causing the scattering of humanity across the earth.
• ABRAHAMIC COVENANTS OF PROMISE – With man proven as a failure in and of himself, God called out one man, Abram, with whom he made multiple covenants, that are one sided promises of blessing that God would accomplish. God promised that His seed would bless all the families of the earth. As Abraham, his lineage produced the “children of Israel (Jacob)” who due to unbelief wound up in bondage to Pharoah in Egypt. Yet, it is through this line that the Son of God, Jesus of Nazareth would ultimately come in Biblical fulfillment.
• THE LAW – After 400 years God miraculously liberated the children of Israel from Egypt and gave them “The Law” to make them “a peculiar people” as the ‘Nation Israel.’ The Law is a Performance-based Acceptance System, not grace. The Nation Israel consistently rejected Jehovah God and His prophets in the Old Testament. Then they called for the death of their Messiah, Jesus, and again later in Acts 7 they rejected ‘the word of the Holy Spirit’ through Stephen, this was ‘the unforgiveable sin.” With that Israel had ‘fallen’ and will be fallen, set aside by God for a time, “until the times of the Gentiles be fulfilled” at the Rapture. (cf. Rom. 11:10-11, 15, 25).
• GRACE – With “the fall of Israel,” God then called and saved his one-time enemy Saul of Tarsus, later called Paul, “the Apostle to the Gentiles.” (Rom. 11:13). Paul received “the revelation of the Mystery” of Christ, directly from the ascended Christ, giving Paul and us the full meaning of the cross for “all men” of all races. All the believers of today’s age of “the grace of God” are members of “the church” that Paul calls “the body of Christ,” destined to be Raptured to dwell “eternal in the heavens” (cf. 1Thes. 4:15-15, 1Cor. 15:51-55, 2Cor 5:1). Following the Rapture of “the body of Christ,” relatively soon thereafter begins the 7-year Tribulation period of divine judgments upon the earth, upon the unbelievers of Israel and the world in which 2/3’s of humanity will die. This ends with the 2^nd coming of Christ from heaven to save Israel and set up His Millennial Kingdom on earth.
• The Millennial Kingdom of Christ on Earth – Christ will rule the world with Israel and with “a rod of iron.” All the while the Devil is at that time locked in the pit. At the end of the Millennium the Devil is released. The unbelievers born during the Millennial period will be gathered by the Devil to make war against the Lord and “the Holy City [Jerusalem].” But, the “fire of God” will come down and “devour them” (Rev. 20:9). This then is followed by ‘the Great White Throne Judgment’ of all the lost humanity of all ages. Being found wanting, their names not found in “the Lamb’s Book of Life,” they will be cast into “the lake of fire” coming to “everlasting destruction” (cf. 2Thes 1:9). With the beast, the false prophet, Satan, Sin, death, and the grave destroyed, Then the “New Jerusalem” will come down from the New Heaven to the Renewed Earth.
• The Eternal Kingdoms of the New Heaven and the New Earth, which are God’s One Kingdom;

“That in the DISPENSATION of the Fulness of Times he [God] might gather together IN ONE all things IN CHRIST, both which are IN heaven, and which are ON earth; even in him:” (Ephesians 1:10 (KJV)

We see how man is unrighteous in and of himself, but God, who is rich in mercy is faithful in Grace to fulfill His promises and do for man what man cannot do for himself.