(15) Let us therefore, as many as be perfect, be thus minded: and if in any thing ye be otherwise minded, God shall reveal even this unto you.
Perfect in greek means teleios, to be fully grown, mature.
The hebrew word for pefect is tamim. To be blamless, whole, sincerity, upright and perfect without defect.
Study 16-19
(16) Nevertheless, whereto we have already atained, let us walk by the same rule, let us mind the same thing.
(17) Bretheren, be followers together of me, and mark them which walk so as ye have us for an example.
(18) (For many walk, of whom I have told you often, and now tell you even weeping, that they are the enemies of the cross of Christ:
(19) Whose end is destruction, whose God is their belly, and whose glory is in their shame, who mind earthly things.
(20) For our conversation is in heaven; from whence also we look for the Savior, the Lord Jesus Christ:
(21) Who shall change our vile body, that it may be fashioned like unto his glorious body, according to the working whereby he is able even to subdue all things unto himself.