“Not that I have already attained, or am already perfected.” (12a). Thankfully, the heresy that one can be perfected in this life, has never been very popular. Most people, including the regenerate, know all too well the imperfection. However, this does not mean that we give up. Instead we saints are equipped by God to press on, to “lay hold of that for which Christ Jesus has also laid hold of” us. (12b) Make no mistake, as in Romans 7, Paul was writing as a brother to ‘brethren’ (13a). The whole family of God is registered in Heaven (Heb. 12:23), both the church militant on earth, and triumphant in heaven, and knowing that we are still in a fight, but will one day join the triumphant, inspires us by God’s Spirit to all press on.
However, being aware of our past failings should not leave us in a morbid self-imposed lifelong penance, such as in the Roman cult, which extends even to the afterlife in purgatory. Instead, we are to look to Christ, by whom we can forgive ourselves and others, and “forgetting those things which are behind and reaching forward to those things which are ahead,” we can “press toward the goal for the prize of the upward call of God in Christ Jesus.” (13b-14) The NGSB* puts this already-not yet in Paul quite well. “The prize of salvation in its fullness has not yet been won, a point Paul emphasizes against ideas of perfectionism (cf. 1 Cor. 4:8; 2 Tim. 2:18; 1 John 1:8). Yet the saving process will be consummated on the day of Christ (1:6, 10). (1879-80).
‘Therefore’ always directs one to the argument that has come before, so the above is the basis for what Paul now adds. “Let us,” expresses what is known as the hortatory subjunctive in Greek, where the author or speaker is exhorting the audience to join them (15a). However, Paul makes clear that one must be mature (15b), and this is made possible only through the wisdom of scripture (cf. I Cor. 2:6-21). The truth we need from God is that which He reveals to us in his word (15c). This is what Paul, as a New Testament documents apostle, was delivering. Being “of the same mind,” means knowing and living by this infallible inerrant and sufficient rule (16). We live by advancing degrees, toward the goal of perfection ‘in’ Christ.
*New Geneva Study Bible (NKJV)