This is an excellent question. I’d like to begin with the “lukewarm” Christian. Let’s read Revelation 3:15-16 where the Lord Jesus is addressing the church of the Laodiceans: “I know your works, that you are neither cold nor hot. I could wish you were cold or hot. So then, because you are LUKEWARM, and neither cold nor hot, I will vomit you out of My mouth” (NKJV). This is the only reference in the New Testament where the Holy Spirit uses the word “lukewarm” to describe those who had professed to be Christians. The Laodicean church was so “nauseating” to the Lord that He informs them that He will ultimately REJECT THEM (this is implied in the words, “I will vomit you out of My mouth).” This suggests that those in the Laodicean church were only Christian “in name,” but NOT “in reality.” They were MERE PROFESSORS who had never really trusted in Christ as their personal Savior. This view is confirmed in verses 17-18: “Because you SAY, ‘I am rich, have become wealthy, and have need of nothing’—and do not know that you are wretched, miserable, poor, blind, and naked—I counsel you to buy from Me gold refined in the fire, that you may be rich; and white garments, that you may be clothed, that the shame of your nakedness may not be revealed; and anoint your eyes with eye salve, that you may see.” This church was made up of members who were PROUD and SELF-SUFFICIENT, thinking they had “need of nothing.” Yet the Lord exposes them by telling them they were actually POOR, NAKED, and BLIND! These words describe their true spiritual condition; they are WITHOUT CHRIST. They claimed to be Christians, but their works proved otherwise. Yet the Lord does recognize that there were some true believers among them. He addresses them in verses 19-20, “As many as I love, I rebuke and chasten. Therefore be zealous and repent. Behold, I stand at the door and knock. If anyone hears My voice and opens the door, I will come in to him and dine with him, and he with Me.” Their hearts had been influenced by the lukewarm conditions that existed in Laodicea and thus the Lord Jesus chastens them and tells them to repent. If they would repent, fellowship with Christ would be restored, for He promises them, “I will come in to him and dine with him, and he with Me.”

The “carnal Christian” is seen in 1st Corinthians 3:1-3: “And I, brethren, could not speak to you as to spiritual people but as to CARNAL, as to babes in Christ. I fed you with milk and not with solid food; for until now you were not able to receive it, and even now you are still not able, for you are still CARNAL. For where there are envy, strife, and divisions among you, are you not CARNAL and behaving like mere men?” The word “carnal” means “fleshly,” which speaks of a believer who is “controlled by his FALLEN HUMAN NATURE.” It is in contrast to the word “spiritual” which describes a believer who is “controlled by the HOLY SPIRIT.” Paul had to rebuke the Corinthian believers for still being in a condition where they couldn’t receive spiritual instruction. They were “still carnal,” which was evidenced by the envy, strife and divisions among them. These things characterize unsaved men and thus they were behaving like those who had never trusted Christ. This is a sad and deplorable condition, for a believer should be living for Christ and not for himself. When one is living to gratify their old, corrupt fallen nature THEY ARE CARNAL, for they are being “led by their fallen nature” instead of being “led by the Holy Spirit.”

So, what is the difference between the carnal Christian and the lukewarm Christian? Technically, we have seen that there really is no such thing as a “lukewarm Christian,” for to be lukewarm is to be totally indifferent to Christ, independent of Christ, and in a future day, to be rejected by Christ. Yet a Christian can be influenced by this condition and will need to repent in order to enjoy fellowship with Christ once again. In contrast to a LUKEWARM condition (where one is neither HOT or COLD towards Christ), the “carnal Christian” is most definitely COLD towards Christ, for they are living to please their selfish, human nature instead of allowing the Holy Spirit to lead them to glorify Christ. A believer in this condition will also need to repent in order to enjoy fellowship with Christ and to be led of the Spirit instead of their fleshly nature. (229.9) (DO)