Question: "What is a carnal Christian?"
Answer: Can a true Christian be carnal? In answering this question, let’s first define the term carnal. The word carnal is translated from the Greek word sarkikos, which literally means "fleshly." This descriptive word is seen in the context of Christians in 1 Corinthians 3:1-3. In this passage the Apostle Paul is addressing the readers as "brethren," a term Paul uses almost exclusively to refer to other Christians, and then goes on to describe them as "carnal." Therefore, we can conclude that Christians can be carnal. The Bible is absolutely clear that no one is sinless (1 John 1:8). Every time we sin, we are acting carnally.
The key thing to understand is that while a Christian can be, for a time, carnal, a true Christian will not remain carnal for a lifetime. Some have abused the idea of a “carnal Christian” by saying that it is possible for people to come to faith in Christ and then proceed to live the rest of their lives in a completely carnal manner, with no evidence of being “born again” or a “new creation” (2 Corinthians 5:17). Such a concept is completely unbiblical. James 2 makes it abundantly clear that genuine faith will always result in works. Ephesians 2:8-10 declares that, while we are saved by grace alone through faith alone, salvation will result in works. Can a Christian, in a time of failure and/or rebellion, appear to be carnal? Yes. Will a true Christian remain carnal? No.
Since eternal security is a fact of Scripture, even the carnal Christian is still saved. Salvation cannot be lost, because salvation is a gift of God that He won't take away (see John 10:28; Romans 8:37-39; 1 John 5:13). Even in 1 Corinthians 3:15, the carnal Christian is assured of salvation: "If anyone's work is burned, he will suffer loss; but he himself will be saved, yet so as through fire." The question often is not whether a person has lost his salvation, but whether a person was truly saved in the first place (1 John 2:19).
For Christians who become carnal in their behavior, God lovingly disciplines them (Hebrews 12:5-11), so they can be restored to close fellowship with Him and be trained to obey Him. God’s desire in saving us is that we would progressively grow closer to the image of Christ (Romans 12:1-2), becoming increasingly spiritual and decreasingly carnal, a process known as sanctification. Until we are delivered from our sinful flesh, there will be outbreaks of carnality. For a genuine believer in Christ, though, these outbreaks of carnality will be the exception, not the rule.