There is room within orthodoxy Christianity to disagree over points in hamartiology, but an orthodox Christian should recognize immediately the false view that we spiritually earn a death sentence when we first sin. The biblical doctrine of spiritual death will be considered here from two angles: first the Godward side and then the manward side.
God is infinitely holy and cannot have a relationship with that which is unholy (Hab. 1:3). His character is one of righteousness and justice (Ps. 97:2). Ultimately, judgment will be the method by which God permanently separates unrighteous men from Himself (Rev. 20:11–15). When we talk about God’s holiness, we speak of His separation from that which is unholy (Heb. 7:26), for “apartness from the profane” is the essential meaning of “holiness.” When we talk about someone being spiritually dead, we include his inherent separation from God, for “separation” is the essential concept of “death” in the Bible. The end result of spiritual death is departure into the Lake of Fire, hence the term, “second death” (Rev. 20:14). This is the Godward side of spiritual death: God is separate from that which is spiritually dead.
Man is born with this death sentence, but is saved when he believes in Christ (Eph. 2:8). There is nothing that a man can do today to earn a spiritual death sentence. This is the manward side of spiritual death: upon conception, we are all spiritual stillbirths.
Here are some biblical reasons for my position regarding the manward side of spiritual death:
The Bible says, “while we were yet sinners, Christ died for us” (Rom. 5:8b KJV), so we are “sinners” by default. The Greek term, “sinner” in Romans 5:8 is the adjective, hamartolos, as opposed to a verb, like the participle, pisteuon “one who believes” in John 3:16. That is to say, we aren’t just “the ones who commit sins” but rather, we are sinful by default, and while we were in this way, Christ died for us (Rom. 5:8). Christ did not wait for us to commit a sin, He died before we were even born because we are inherently sinful. This is our natural state and so we start out separate from God, that is, we are spiritually dead even upon conception.
The Bible speaks of us in terms of death. A man is born spiritually dead, but when he believes in Christ for eternal life, he is born again (John 3:1–15) and this resolves his spiritually dead state. It is proper to speak of this second birth (or regeneration) as a salvation (Titus 3:5), since it saves man from the condemnation. This condemnation is spoken of in terms of perishing (John 3:16–18) as it is the result of spiritual death. There is no indication that this death begins after we are born, but to the contrary, it is always the default.
For example, David writes under the inspiration of the Holy Spirit, “Behold, I was brought forth in iniquity, And in sin my mother conceived me” (Psalm 51:5). David is not blaming his mother for his sin, but rather acknowledging his own sinfulness (51:3). We are not born naturally holy, but naturally sinful and separate from God; this is our default setting even in the womb.
Some would say that ignorance means innocence, but the Bible says that ignorance and blindness are not excuses (Eph. 4:18). Pelagianism was an ancient heresy that proposed that man becomes dead through repeated sinning, but Paul says that unbelievers walk in their sin because they are dead (Eph. 2:1–10). Being dead, we walked in trespasses and sins; Pelagianism and similar views put the carriage before the horse by saying that we become dead when we trespass or sin.
The Bible also says that in Adam, all die (1 Cor. 15:22). To say that we get this death sentence when we first sin is to say that we are not born in Adam, but somehow transferred to Adam when we first sin. This doctrine would be at odds with the faith-based assurance that the Bible so clearly proclaims; instead of a person turning to Christ to determine if he is saved, he could examine himself to see if he has sinned.
Man is inherently in need of eternal life. The only thing that man can do to be saved is to believe in Christ for eternal life (which is not doing anything per se, but rather believing). Just as our good deeds did not make us spiritually alive, our bad deeds did not make us spiritually dead; we were already dead.