Unbelievers certainly are in the equation.
John 3:18 - He who
believes in Him is not condemned; (BELIEVERS) but he who
does not believe is condemned already, (UNBELIEVERS)
because he has not believed in the name of the only begotten Son of God.
Unbelievers will certainly be judged and condemned (Revelation 20:11-15) and some (like these scribes and Pharisees) will receive
greater condemnation according to Jesus (Matthew 13:24). Believers will be judged according to their works in order to receive
rewards and loss of rewards and
not condemnation (1 Corinthians 3:11-15). God's people are not divided up into two separate camps. There are only sheep (believers) and goats (unbelievers) - John 3:18. There are no shoats! Believers are
described as
"those who by patient continuance in doing good seek for glory, honor, and immortality...everyone who does good" (Romans 2:7,10).
Unbelievers are
described as
"those who are self-seeking and do not obey the truth, but obey unrighteousness...everyone who does evil." (Romans 2:8,9).
You need to stop reading scripture through the lens of performance based works salvation. It leads to self righteous conclusions and confusion. If a person’s intent is to live according to the flesh, it’s an indication they are not saved. Yet if a person, by the Spirit is putting to death the deeds of the body, it's an indication they are saved.
Romans 8:13 (AMP) - for if you are living according to the [impulses of the] flesh, you are going to die. But if [you are living] by the [power of the Holy] Spirit you are habitually putting to death the sinful deeds of the body, you will [really] live forever.
Also, just because a letter is addressed to "brethren" does not mean that everyone in a group of "professing" believers is a genuine believer. It's not difficult to find wolves in sheep's clothing among the sheep, even on various Christian Bible discussion forums. *How about some context:
Romans 8:5 - For
those who live according to the flesh set their minds on the things of the flesh, but
those who live according to the Spirit, the things of the Spirit. 6 For to be
carnally minded is death, but to be
spiritually minded is life and peace. 7 Because the
carnal mind is enmity against God; for it is not subject to the law of God, nor indeed can be. 8 So then,
those who are in the flesh cannot please God. 9 But
you are not in the flesh but in the Spirit, if indeed the Spirit of God dwells in you. Now if
anyone does not have the Spirit of Christ, he is not His. 10 And
if Christ is in you, the body is dead because of sin, but the Spirit is life because of righteousness. 11 But
if the Spirit of Him who raised Jesus from the dead dwells in you, He who raised Christ from the dead will also give life to your mortal bodies through His Spirit who dwells in you. 12 Therefore, brethren, we are debtors--not to the flesh, to live according to the flesh.
Paul sets up a CONTRAST between those who
live according to the flesh (unbelievers/false brethren) and those who
live according to the Spirit (believers). In verses 8-9, Paul clearly states - So then,
those who are in the flesh cannot please God. 9
But you are not in the flesh but in the Spirit, if indeed the Spirit of God dwells in you. Now
if anyone does not have the Spirit of Christ, he is not His. See the
Contrast? Now of course Paul is writing to believers (yet it's not hard to find unbelievers/false brethren mixed in with a group of believers) as we see all throughout scripture. (Matthew 7:15-23; 13:24-30; John 6:64-71; 1 John 2:19; Galatians 2:4; Jude 1:3-24 etc..).
So there are distinctively two groups in
Romans 8. The present tense is used to denote lifestyles. Those
consistently walking according to the flesh in verse 5 are linked to
"being in the flesh" in verse 8. And those who
"walk according to the Spirit" in verse 5 are linked to
"those who are no longer in the flesh" in verse 9. *Tell me you understand this.
Yes, this is
descriptive of those who are in Christ/believers.
So once again we see the
CONTRAST between those who will receive eternal life (those who by patient continuance in doing good seek for glory, honor, and immortality...everyone who works what is good -
descriptive of BELIEVERS) and those who will not receive eternal life (those who are self seeking and do not obey the truth, but obey unrighteousness...every soul of man who does evil -
descriptive of UNBELIEVERS).