People often need proof to believe something. "Seeing is believing".
In the 16th centrury, a method of determining alcohol content was often used by soaking gun powder with the rum or whiskey. If the gun powder could be ignited, then that was considered "proof" that the alcohol had not been watered down. This method was standardized in the U.S. in 1848. 50% alcohol by volume (ABV) was considered 100 proof.
The Apostle Thomas wanted proof. He needed to see and touch (John 20:24-25).
When Jesus appeared to the Apostles in a locked room, He invited Thomas to put his fingers in the holes in His hands and to touch His side where He had been speared. Thomas' reaction was beautiful (John20:28), "My Lord and my God!"
Jesus' answer to Thomas was quite scathing, in my opinion. "Have you believed because you have seen me? Blessed are those who have not seen and yet have believed."
If you have to have evidence before you believe, then you don't trust anything the Apostles have written as eye witnesses. The Gospel of Jesus Christ requires faith to believe. Faith is the key to receiving the righteousnous of Christ Jesus (Genesis 15:3-6 and 1 Peter 1:8-9).
We believe because of the hope Jesus holds out. We believe because our Great God has made a way for us to escape His wrath and to be able to stand in the presence of His Glory (Jude 1:24). We believe because of the goal set before us (2 Corinthians 4:16-18) so we can keep moving forward, not blindly, but by faith (2 Corinthians 5:7).
Because in Christ, there is joy and peace in all circumstances (John 16:33 and 1 Peter 1:8).
Soon, this life will be a very distant memory (Isaiah 51:6 and Revelation 21:1-4). So we have not seen, but we believe.
God is AWESOME!