How does Romans 8 define what it means when it says, "walk after the flesh"?
It does. How?
Much love!
It’s called studying the scriptures, all of them on a subject, not isolated proof texts - and it’s very easy to find where Paul defines what walking in the flesh means, along with the the penalty of doing that, of not entering heaven, such as below where He contrasts walking in the spirit , same phrase as in Romans 8:1, with works of the flesh.
Gal 5:16 This - I say then,
Walk in the Spirit, and ye shall not fulfil the lust of the flesh.
Gal 5:17 For the flesh lusteth against the Spirit, and the Spirit against the flesh: and these are contrary the one to the other: so that ye cannot do the things that ye would.
Gal 5:18 But IF ye be led of the Spirit, ye are not under the law.
Gal 5:19 Now the WORKS OF THE FLESH are manifest, which are these; Adultery, fornication, uncleanness, lasciviousness,
Gal 5:20 Idolatry, witchcraft, hatred, variance, emulations, wrath, strife, seditions, heresies,
Gal 5:21 Envyings, murders, drunkenness, revellings, and such like: of the which I tell YOU again, as I have also told youin time past, that they which DO such things shall NOT inherit the kingdom of God.
Sexual sins of adultery and fornication are first on the list of works of the flesh, and it’s evident in scripture that living a lifestyle of sexual sins makes a believer Gods enemy:
Rom 8:5 For they that are after the flesh do mind the things of the flesh; but they that are after the Spirit the things of the Spirit.
Rom 8:6 For to be carnally minded is death, but to be spiritually minded is - LIFE -and peace.
Rom 8:7 Because the carnal mind is ENMITY against God: for it is not subject to the law of God, neither indeed can be.
Rom 8:8 So then they that are in the flesh cannot please God.
IN Verse 8:7 above, Paul warns above, that having a carnal mind is ENMITY against God, meaning you actually become Gods ENEMY.
James agrees:
Jas 4:4 Ye adulterers and adulteresses, know ye not that the friendship of the world is ENMITY with God? whosoever therefore will be a FRIEND OF THE WORLD is the ENEMY of God.
The next verse makes clear that the warning against living a lifestyle of sexual sins is to the BRETHREN:
1Th 4:3 For this is the will of God,
your sanctification: that you abstain from sexual immorality;
1Th 4:4 that each one of you know how to control his own body in holiness and honor,
1Th 4:5 not in the passion of lust like the Gentiles who do not know God;
1Th 4:6 that no one transgress and wrong his BROTHER in this matter, because the Lord is an avenger in all these things, as we told you beforehand and solemnly WARNED you.
1Th 4:7 For God has not called us for impurity, but in holiness.
1Th 4:8 Therefore whoever disregards this, disregards not man but God, who gives his Holy Spirit to you.
It all comes down to the fact that, we are required after salvation to continue in the same faith and repentance (turning away from living willfully in sin) that we had when we were saved.