By the context we can see that Paul is speaking about Christians being in the flesh:
"Therefore, brethren, we are debtors, not to the flesh, to live after the flesh. For if ye live after the flesh, ye shall die: but if ye through the Spirit do mortify the deeds of the body, ye shall live" (Ro.8:12-13).
If a Christian lives after the flesh and are not led by the Spirit then they cannot please God.
Those in the flesh cannot please God. Everyone by nature are in the flesh !
Paul plainly says believers are not in the flesh Rom 8:9
[FONT="]But ye are not in the flesh, but in the Spirit, if so be that the Spirit of God dwell in you. Now if any man have not the Spirit of Christ, he is none of his.[/FONT]