"If Christ has not been raised [from the dead], your faith is futile; you are still in your sins." (1 Cor. 15:17)
Everything in Christianity hinges on the resurrection of Jesus. Paul understood that when he wrote these words. Anybody could claim to be God; he may even be able to do a few tricks or deceive a few people to convince them that he is God. He could anger the right people and then proclaim that they would kill him and his death would bring eternal life for his followers. In fact, there have been many people throughout history that have done just that. The problem is that their story ends at their grave.
The proof that Jesus is more than an misunderstood teacher, a raving lunatic, or an egotistical deceiver lies in the resurrection. Jesus repeatedly declared that He would rise three days after his death. They may not have understood it, but even his enemies remembered that He had said it (see Matt. 27:62-66). Jesus would rise from death and it is the great sign that He is indeed God come to save us.
Even then, the Jewish religious leaders understood how important this was. They posted guards to protect the tomb and did everything within their power to prevent Jesus from coming out. The other Gospels tell us that God simply overcame all of their efforts (Matt. 28, Mark 16, Luke 24). At the same time, the Jewish leaders set up people to lie to cover up for what had happened. They paid the Roman guards to lie and say that Jesus' disciples stole the body (Matt. 28:11-15). This and other stories are still circulated today in an attempt to disprove the resurrection.
Jesus did not simply disappear. Instead, He spent 40 days appearing to His followers to prove what had happened. The Resurrection is one of the best-attested miracles that Jesus performed. Paul tells us in 1 Cor. 15, that Jesus appeared to Peter, to the twelve disciples, to James (his brother, who could make a positive ID), to him, and to five hundred of his followers. Paul says that most of these people are still alive, go ask them. Jesus appeared to the disciples and ate fish, allowed them to see the marks of his injuries, and continued to teach them. This was not something that happened in the dark and was kept a secret. In fact, one of the most compelling arguments for the resurrection is that all Jesus' opposition had to do to prove it was false was to show the body. If they had simply brought out the body of Jesus, the argument is over. There are no followers and there is no Christianity. But they didn't. Because they couldn't.
What does the Resurrection mean? It means everything. To take Paul's earlier statement and argue it from the other perspective, Christ has been raised, so our faith is effective and our sins are forgiven. As a result of it, Jesus' often cowardly followers are willing to die for His message. Who would die for a lie? Their lives are transformed.
The Resurrection is the capstone for Jesus' argument that He is God. He has demonstrated God's power through the miracles that He worked; even those who oppose Him have to admit that no mere man can do the things that He does. Now He has risen from a brutal death to prove that He is God. Now many find themselves in the place of Thomas, they hear and want to believe, but just can't. So Jesus proves Himself to them in practical experience. John says he wrote this book to prove that Jesus is the Christ, the Son of God. The point is that you would believe. It is all futile unless we believe that it is true.
For those who believe, Jesus gives life. For those who are truly seeking Him, Jesus reveals Himself. Do you need to express faith in Him today and receive His forgiveness? Do you need to honestly express areas where you are still seeking and questioning? Jesus will reveal Himself to those with honest questions and doubts. Keep seeking Him through the Bible and He will make it clear to you.
Jesus' desire is that you will believe in Him. And when you believe in Him, you will have life in Him.