Sin is disobedience to God’s will. It encompasses both wrong belief and wrong behaviour, as God wills that both are exercised rightly (Romans 1:18-32). It also encompasses both our motives and actions because even outwardly respectable deeds are not truly good unless done for the glory of God (Romans 14:23). Even the smallest sin is therefore hugely serious in reflecting our stubborn rebellion against God.
Sin infects the entirety of our being—total depravity (Genesis 6:5). We are not as bad as we could be, but our minds, hearts and wills are all tainted, and so our reason, emotions, and desires are untrustworthy. In terms of pleasing God, this entails total inability: We love sin so much that we are quite simply unable to accept the gospel, respond with faith, or obey God’s will unless he enables us to do so (Romans 3:10-11, 8:7-8, 1 Corinthians 2:14, 2 Corinthians 4:4). This is why the New Testament uses ideas of blindness, deafness, slavery and death to describe sin (Mark 8:18, John 8:34, Ephesians 2:1). Each implies inability—to seeing or hearing the truth, or being free to live a righteous life.
Sin is directly linked to whether or not we are prepared to trust what God says or go with our own desires (Genesis 3:1-6). At its heart it is the proud assumption that we should determine what is good and evil rather than God (Genesis 2:17). We would be wise then to reject anything that contradicts the bible, and be highly suspicious of acting on what merely seems or “feels right” to us.
The punishment for sin is death. At one level this refers simply to the separation of body and spirit. Spiritually however, it is to endure God’s curse and be shut off from his blessing (Genesis 3:16-24, Galatians 3:13). This is seen first in the death of physical and moral decay (Romans 1:18-32, Ephesians 2:1). In his wisdom God considered it right to have Adam represent the human race. This meant we were also somehow included in his disobedience. So from conception, his descendents experience the curse of death in their susceptibility to sickness and their disposition to sin (Romans 5:12-19, 1 Corinthians 15:22, Psalm 51:5). All illness, evil, and the suffering that results therefore stem in some way from God’s punishment of our race “in Adam.”
Original sin refers to how the sin of every human being stems from this origin. Humanity was not created sinful by God, but made itself sinful (Romans 5:12). If you like, Adams actions distorted the moral mould his descendents were to come from. However we are still held responsible by God because we willingly follow the sinful desires we inherit from Adam (Romans 2:6, Ephesians 2:3).
God holds off death’s full experience throughout our lifetimes so that we may turn to him (2 Peter 3:9). Every blessing we receive in life is therefore an undeserved gift of his grace (Matthew 5:43-45). Those who fail to respond to the gospel will however endure death’s most horrific expression in hell—the second death (2 Thessalonians 1:6-10, Revelation 20:13-15). Jesus was clear about hell: Though he hinted that people’s experience of it would justly vary according to their sin, he still portrayed it as an appalling place of agonising torment and utter destruction (Mark 9:48, Matthew 10:28, 11:20-24, 25:30, 41, 46 cf. Luke 16:23-24). He wanted people to fear God’s wrath so that they would do their utmost to escape it (Matthew 10:28, Mark 9:42-49).