There are many people in the world with differing views of what is a Christian. Indeed much good and much evil has been done using that name of Christ. It is not my intent to redefine political boundaries or religions but to communicate the basic underlying message believed by Christians of the years shortly after the death, burial and resurrection of Christ and the true church of today.
A Christian is one who understands and believes something like the following:
1. The Holy Bible is God's written message to man, the authority for right living and the foundation for knowledge of God, truth and error.
2. God is a Spirit, infinite, eternal, and unchangeable in His being, wisdom, power, holiness, justice, goodness, and truth. God is unerringly right, always does what is right, and is just - meaning He always repays wrong, no exceptions. God knows everything. God is good and cannot do wrong.
3. Each man and woman is individually accountable to God.
Note that God's glory is the standard by which we are judged. Not the guy down the street. Each man and woman has violated God's commands, so each stands condemned before God's perfect, righteous judgment.
In other words, the pay for sin is physical, spiritual, and eternal separation from God and His goodness. Pay day will come.
4. God has made a provision for each man's sin through a sacrifice. That is, a sacrifice has been given in payment for sin that was sufficient to satisfy God's anger against your sin. That payment was the sacrifice of God in the flesh, the perfect, sinless, Son of God. He who had no sin, no death due Him, came to earth to die that God's anger against you might be satisfied.
Christ died, was buried, and rose again from the dead, proving His power over death and His promise of life to those who will believe.
5. You must trust in God's provision for your sin, not your own provision. There is Nothing, absolutely nothing, that you can do to save yourself. This is Good News! You must trust in the sacrificial gift of His Son as the completed and total payment for all your sins, past, present, future. John 3:18 He that believeth on him is not condemned: but he that believeth not is condemned already, because he hath not believed in the name of the only begotten Son of God.
Ultimately, a Christian is a person who has recognized his or her position as a condemned sinner before the only true God, and, having come up short, has placed himself or herself upon God's mercy, trusting alone in Jesus Christ's payment on the cross as sufficient to satisfy God's righteous anger against his or her sin.