Fesko begins chapter 3 by stating:
Whenever we consider any doctrine within the loci of systematic theology, we must locate the doctrine within the scope of redemptive history. To restate this principle in technical terms, we must properly locate the ordo salutis within the historia salutis (p93)
Failure to do this can result in a divorce of our system of redemption from the acts of God in salvation history. For example, someone might say, "I'm not too bothered whether you believe in the resurrection or not. I'm bothered about whether you're growing in a personal relationship with Jesus."
Throughout the chapter Fesko presses home that eschatology is not simply the period immediately before the return of Christ, but the entire era from Christ's first appearing through to his second. So the period of the church, in which we all live, is an eschatological period. The OT prophets were expecting the Messiah to usher in the new creation during 'the last days' (LXX Gen. 49:1). The "last days" then, refer to the end of the old era of sin and death and to the beginning of a new creation.
Fesko notes that in the OT, the last days contain both favourable and unfavourable events, blessing and curses, joy and tribulation. These contrasting states hint at the already-not yet aspect of the eschatological age (p98).
In the NT, particularly in Paul's writings, we see juxtapositions of the protologcial and the eschatological, particularly in Romans 5 and 1 Corinthians 15 where the first and last Adams are contrasted. The first Adam is of the earth and ushers in death. The second Adam is of heaven and ushers in the re-creating power of the Holy Spirit.
Three implications for justification follow. First that Christology, pneumatology and eschatology are inextricably intertwined (p104). That is, Christ accomplishes redemption, the Spirit applies it and this is the first act of new creation. Second, and this blew my mind, justification is eschatological. Therefore, the judgement of the last day has been brought forward for those in Christ and a "not guilty/righteous" verdict has been rendered on our behalf because of Christ. That judgement is final. We can have complete assurance of entrance to the heavenly kingdom. Third, there is an already-not yet tension to our redemption. We are completely and irreversably justified. Nevertheless, we still struggle with the sin present in our mortal bodies.
It was refreshing to read an approach to salvation that is so Christ focused and historically grounded. What an antidote to the mystical piety of those who sing, "You ask me how I know he lives? He lives within my heart." Bull. I know he lives because of the self-authenticating word of God, confirmed by the outpoured Spirit of the resurrected Christ. I know he lives because he is ushering in a new creation, of which believers are the firstfruits. I know he lives because I'm counted righteous in Christ, forever, apart from my works. I know he lives because I struggle with sin in this already-not yet state. Before it wasn't a struggle. I just did it. Dude, if you're uncertain of your faith and wondering whether you're a Christian or not, you need to get a grasp of the doctrine of justification.