When I go into public high schools as a Christian worker, I am very often asked by the school students whether smoking, swearing, abortion, pre-marital sex, etc, etc, etc, are sins. The idea of sin seems to be a huge concern for many teenagers. Various factors, such as increasing levels of freedom and independence, surging hormones, peer pressure and media influences, as well as underdeveloped levels of self-discipline, can mean that teenagers engage in activities that they know to be wrong and unhealthy.
I find it interesting that the concept of sin is still understood, and is very real, for young people in post-modern society. However I am disappointed by these “sin questions” from high-schoolers because they reveal a very narrow view of sin, and no real comprehension that Jesus has provided the solution for the sin problem with his redemptive death on the cross.
When these “sin questions” come up, I try to redirect and refocus the subject – without minimising their concerns – by pointing out that ultimately there is only one sin that really matters. John made this very clear in his gospel when he quoted Jesus.
“Whoever believes in him is not condemned, but whoever does not believe stands condemned already because he has not believed in the name of God’s One and Only Son” John 3:18.
“Whoever believes in the Son has eternal life, but whoever rejects the Son will not see life, for God’s anger remains on him” John 3:36.
The ultimate sin is not believing in Jesus. Not believing in Jesus is the same as rejecting him. As far as salvation and eternal life goes, unbelief is the sin that really matters! 
While stating plainly that condemnation is the consequence of unbelief, John, quoting Jesus, did not focus on this sin. Instead, he wanted to focus on the antidote: belief – and the new, abundant and eternal life that comes from faith.
“For God so loved the world that he gave his One and Only Son that whoever is believes in him will not perish but have eternal life” John 3:16.
“. . . everyone who believes in him will have eternal life” John 3:15.
“I have come that they may have life and have it to the full” John 10:10b.
John wrote his whole gospel with the hope that people reading it would believe in Jesus and receive eternal life as children of God.
“But these things are written so that you may believe that Jesus is the Messiah, the Son of God, and that by believing you may have life in his name” John 20:31.
“To all who receive [Jesus] to those who believe in his name, God gave the right to become children of God” John 1:12.
What does it mean to believe?
The Greek word for believe is typically used in a continuous tense by John and means “keep believing, keep trusting, keep having faith”. True belief and faith is not just a mental or intellectual thought, attitude or acknowledgement. It involves entrusting your life to Jesus. When someone arrives at the point when they can fully place their faith in Jesus, they become spiritually alive. (Instead of being spiritually dead.)
“I tell you the truth whoever hears my words and believes him who sent me has eternal life and will not be condemned; that person has crossed over from death to life” John 5:24.
When we put our faith in Jesus we receive salvation. We enter into a new, eternal life in relationship with God, and God completely forgives and pardons all our sins. (Compare John 5:24 with Acts 26:18; Colossians 1:13-14; 1 John 3:14.)
God doesn’t want us to sin. He doesn’t want us to do things that are wrong and unhealthy: things that hurt and damage ourselves, other people, society, and the planet. God wants us to live lives that bring his love, healing, hope and restoration. This can only begin when we believe in his Son, Jesus Christ, and experience for ourselves his gift of salvation. 
 The Bible speaks of blasphemy (insults) against the Holy Spirit as the unpardonable sin (Matt 12:31-32; Mark 3:28-30; Luke 12:10). The surrounding context of these verses shows that blasphemy of the Holy Spirit involves ascribing the devil and demonic power to Jesus’ ministry and miracles.
I have not mentioned the sin of blasphemy of the Holy Spirit in this article because people who commit it are most likely very few in number, whereas people who do not believe and trust in Jesus, and thus reject him, are numerous. [If anyone is worried that they may have blasphemed the Holy Spirit, that “worry” is a very good indication that they have not blasphemed the Holy Spirit.]
 Christian faith also involves believing that Jesus is divine and eternal, and came to earth sent from God the Father. Furthermore, Christian faith involves trusting that Jesus is the only one able to save humanity from sin and provide eternal life, because he alone paid the penalty of sin with his sacrificial death on the cross and rose from death. In reality, many Christians come to saving faith in Jesus before fully appreciating these facts.
© 1st of October, 2010; Margaret Mowczko