Jesus made some pretty amazing promises. He claimed to be the Son of God, and said things like, "whoever believes in Me will have everlasting life" (John 6:47). It sounds sounds like a great story, but how can we know that what He said is true?
The Bible says that "without faith it is impossible to please God." But does this mean that we just have to close our eyes and say we believe? On the contrary, there is actually plenty of evidence available such that we can be confident that Jesus' claims are really true.
First of all, we can know with certainty that the gospels in the New Testament are, in fact, eyewitness accounts of Jesus' life and ministry. The books of Matthew and John were written by Jesus' disciples, who were with Him throughout His ministry; the gospel of Mark was written by John Mark, a companion of Peter who faithfully recorded Peter's testimony of Jesus, and the book of Luke was written by a physician and companion of Paul's, who carefully investigated, collected and reported the testimony of those who were eyewitnesses of those events.
We can also be confident of the validity of these testimonies, both in their agreement with one another, and in the absense of dissenting accounts. Jesus had plenty of enemies who would have loved to have discredited the early Christians if any of the facts that were recorded had been untrue. Instead, we see Jewish writings calling Jesus a sorceror who led Israel astray — statements which acknowledge His miracles rather than contradict them — that merely dispute His source of power. We know, furthermore, that the accounts we have in the gospels were not some later mythological development, as they were all written within the lifetimes of various eyewitnesses, including those hostile to Christianity, who, as stated, would have been more than willing to contradict and disprove the claims being made, had they been false.
Finally, we can have great confidence that these documents have been faithfully and accurately preserved. From the dates of the earliest manuscripts to the overwhelming number and agreement of extant copies, the New Testament is unrivaled among ancient writings in the purity of its text as actually transmitted. No other historical document has as many manuscripts dating as close to the original source as we have for the gospels and the other books of the New Testament.
So, being assured that what we have in the gospels is an accurate account, what about Jesus' claim to be the Son of God? He told both His disciples and His opponents that He would give them one proof that He is truly the Messiah, God in the flesh: He declared that He would come back to life 3 days after His death. Again and again He told His disciples that He would be killed, and that He would rise again on the 3rd day. No other person in history has ever made such an audacious claim, much less carried it out.
What about the resurrection, then? First of all, there was never any dispute that, despite the fact that a Roman guard had been posted, the tomb was empty 3 days after the crucifixion. Jesus' enemies never denied that the body had vanished — they simply tried to claim that the disciples had stolen it, Roman guard not withstanding.
Then, you have the fact that Jesus was seen alive after His crucifixion, in the flesh, by over 500 people. He was seen by various people at various times, and in a variety of different circumstances. They saw Him eat and drink, they touched Him... the disciple Thomas even put his hands in the wounds Jesus had received on the cross. Jesus' presence was neither ghost nor vision, and His disciples knew it.
In the words of Gary Habermas, "The Resurrection was undoubtedly the central proclamation of the early church from the very beginning. The earliest Christians didn't just endorse Jesus' teachings; they were convinced they had seen him alive after his crucifixion. That's what changed their lives and started the church. Certainly, since this was their centermost conviction, they would have made absolutely sure that it was true."
This is confirmed by the persecution of the early church. These people, who had seen Jesus alive and knew firsthand that the Resurrection was real, were willing to suffer torture and death rather than deny the truth. It's difficult enough to suffer for one's honest convictions; but you can be absolutely sure that people don't willingly endure the kind of suffering that the early Christians endured for what they know to be a lie.
So what does it mean to say, "without faith it is impossible to please God"? It means accepting the evidence, and trusting in it. There may be alternate theories that try to explain away the Resurrection, but none of them are supported by the weight of evidence we have in favor for it. You have to ask yourself honestly, what explanation best fits the data? There is no legitimate competing hypothesis.
Jesus said, "Come to Me, all you who are weary and heavy-laden, and I will give you rest." He said, "God so loved the world that He gave His one and only Son, that whoever believes in Him shall not perish but have eternal life." He also said, "Whoever comes to me I will never drive away." We can know for certain that His words are true, and we can have hope in Him for eternal life. It's a hope that is not based on our feelings, emotions, or "spiritual" experiences, but a hope that is grounded in fact — the fact that Jesus did live, He did die on the cross for our sins, He did rise from the dead after 3 days, and He does live, eternally, and gives life to those who put their trust in Him.