In one sense, therefore, the church lives in a remarkable tension between what is “already” and what is “not yet”: Christians already enjoy something of the kingdoms beneﬁts—acquittal before God, possession of eternal life, the presence of the Holy Spirit as the down payment of the ﬁnal inheritance, the forgiveness of their sins, deep fellowship with other children of God, assurance that their risen Savior and Lord is already reigning with all of his Father’s authority; yet Christians do not yet enjoy all the blessings that will one day be theirs—the abolition of death, the utter destruction of the power of sin, possession of resurrection bodies, free scope in a new heaven and a new earth, untarnished worship of the triune God, the bliss of undiluted love and unblemished holiness, the perfection of fellowship. Thus, New Testament eschatology is not a restricted focus on the last things but includes the wonderful news that the last things have in certain respects already arrived. New Testament eschatology deals alternately with what is yet to come and with what has shatteringly, unexpectedly, magniﬁcently arrived. In other words, New Testament eschatology is simultaneously futuristic and realized.
Failure to keep the balance breeds not only theological error but also moral and lifestyle problems of considerable severity. Overemphasis on the futuristic aspects of eschatology, e.g., at the expense of the realized aspects, may foster unhealthy speculation regarding what God has not revealed, date-setting as to when Christ will return, a denial of the graces and beneﬁts we have already received, and a depreciation of the importance of living together as Christians who constitute a kind of outpost of the new heaven and new earth. The opposite imbalance may prompt us to neglect the promises the Bible gives us regarding the future, to forget to live lives that look forward to and long for Christ’s return, and to act as if the fullness of all Christ provided by his cross-work is already our due.
D.A. Carson — A Model of Christian Maturity, p. 52