15 Therefore let us, as many as are mature, have this mind; and if in anything you think otherwise, God will reveal even this to you.
16 Nevertheless, to the degree that we have already attained, let us walk by the same rule, let us be of the same mind.
mature (v.15) — (“perfect” in KJV) = that which reaches the end, full-grown
Paul, perhaps, is using irony in light of verse 12 where he says he doesn’t consider himself perfect yet, but he could also be, and probably is, referring to positional perfection in Christ (Colossians 2:10).
Paul was far from practical perfection, but he was a mature Christian because he constantly walked in Christ.
think otherwise (v.15) — think otherwise than they ought to be thinking — thinking they are perfect. Evidently, there were some in the Philippian church who thought themselves sinlessly perfect, with no further spiritual growth needed.
attained (v.16) = (here) arrive at, reach, progress along a road to a certain point. Attain (in verse 12) means “to take or appropriate.
already attained (v.16) — to the point of the level of spiritual maturity we have reached
walk by the same (v.16) = (here) walking with others, walking in step — walking in verse 17 means “walking individually.” The picture is one of walking along a path.
rule (v.16) = measuring rod (this word isn’t in the most authentic manuscripts)
let us be of the same mind (v.16) — not in the most authentic manuscripts