That’s not a question we often ask – and perhaps that’s why so much confusion surrounds it.

It’s not someone who’s been christened, or baptised. Christians should be baptised, but being baptised doesn’t make you a Christian. No ceremony can do that.

It’s not someone who goes to church. Christians should go to church when they’re able, but going to church doesn’t make you a Christian. An interested non-Christian might go to church.

It’s not someone who does good. Christians should do good, but doing good doesn’t make you a Christian. Lots of people who are not Christians do good. It’s not someone who believes in God. Jews, Muslims and others believe in God as well as Christians.

A Christian is someone who has undergone two great changes. They happen at the same time, and they always go together. But because both are so big, it may help to think about them one at a time.

A Christian has had a great change inside them. It’s such a new start that the Bible calls it being ‘born again’ (John 3:3). You can easily be baptized, or go to church, or do good, or believe in God, without being born again.

Someone who has been born again has new attitudes. Where before they had ‘hostility against God’ now they ‘delight in the law of God’ (Romans 8:7 and 7:22). And where before they were unwilling to trust simply in Jesus to put them right with God, now they know they must. We are ‘not justified by keeping God’s law, but by trust in Jesus Christ’ (Galatians 2:16).

A Christian has had a great change outside them – God has forgiven them. When someone has been offended, two things are needed for the relationship to heal. The offender needs to recognize their fault, apologise, and put it right as far as they can. Then the other person needs to forgive them and let it go. It’s just the same between us and God – but there’s a problem.

I said the offender needs to put it right as far as they can. But sometimes, of course, they can’t. If you smash someone’s car you may not be able to replace it. When it comes to us and God, that’s just the problem. We have wronged him, but we can’t put it right, no matter how sorry we are.

That’s why Jesus is God’s greatest gift. Because he is both God and man, he could put things right with God on behalf of his people. And he did, even though it cost his death. We are ‘reconciled to God through the death of his Son’ (Romans 5:10).