The Cultural Mandate given to Adam and Eve at the beginning of the human race is a foundational feature of postmillennial eschatology. As the saying goes: Eschatology is assumed in Protology.” That is, the end is assumed in the beginning.
In yesterday’s post, I showed how the Cultural Mandate supported the postmillennial scheme. Today I will focus on the objection that the Cultural or Creation Mandate was unique for Adam and is no longer operative because of their fall into sin.
But this cannot be, for Scripture often repeats the Creation Mandate. This assertion bothers amillennial scholar Herman Hanko, who argues:
“Adam did not abandon the cultural mandate; sin and the curse made it impossible for Adam to continue it. This is not a mere quibbling over words; this strikes at the very heart of the [millennial] question. Forgotten is the fact that sin and the curse made it forever impossible for the cultural mandate to be fulfilled in this present world.” 
This view overlooks what Scripture actually affirms.
We see the Cultural Mandate in force in both testaments (Ge 9:1ff; Heb 2:5–8). Psalm 8 clearly evidences the Cultural Mandate: “What is man that You are mindful of him, And the son of man that You visit him? For You have made him a little lower than the angels, And You have crowned him with glory and honor. You have made him to have dominion over the works of Your hands; You have put all things under his feet” (Ps 8:4–6).
Postmillennialism’s optimistic expectations comport well with God’s creational purpose. They highlight the divine expectation of the created nature of man qua man. Postmillennialism expects the world as a system (kosmos) to submit to God’s rule by the active, sanctified agency of redeemed man, who is renewed in God’s image (Col 3:10; Eph 4:24). In other words, postmillennial eschatology expects in history (though not perfectly so) what God originally intends for history (man’s ruling the world for God’s glory). It sees God maintaining his plan and moving history toward its original goal, but now on the new basis of his sovereign and gracious redemption. Hanko’s objection to postmillennialism’s employing the Cultural Mandate arises from his deep sense of the genuine fearsome power of sin. The postmillennialist, however, sees God’s continuing the Cultural Mandate on a new principle: the very real and even greater power of redemption in Christ.
Postmillennialism also well answers historic premillennialism’s concern that: “the covenantal unity of the entire Bible demands that the millennial kingdom should be materialized on this earth before the beginning of the new heavens and earth.” 
So then postmillennialism does “acknowledge that Genesis 1:26–28 must be taken as an account of the covenant of blessings/promise.” Indeed, in postmillennialism we see that “Adam, as God’s vice-regent, and his progeny were to put ‘the finishing touches’ on the world God created in Genesis 1 by making it a liveable place for humans. . . . God’s ultimate goal in creation was to magnify his glory throughout the earth by means of his faithful image-bearers inhabiting the world in obedience to the divine mandate.”
1. Herman Hanko, “An Exegetical Refutation of Postmillennialism,” 10.
2. Chung in Craig Blomberg and Sung Wook Chung, Historic Premillennialism, 144.