Hope

One Bible lexicon defines the Greek word for hope (ἐλπίς) as a “joyful and confident expectation of eternal salvation.” In his letter to Roman believers, St. Paul adds to this definition: “For in this hope we were saved. Now hope that is seen is not hope. For who hopes for what he sees? But if we hope for what we do not see, we wait for it with patience.” And then in his letter of encouragement to Titus he speaks of “waiting for our blessed hope, the appearing of the glory of our great God and Savior Jesus Christ.”

So the Christian meaning for hope goes way beyond vague wishful thinking (“I hope it doesn’t rain tomorrow”) and is grounded in a deeper sense in the certainty of what Jesus promises us if we put our faith in Him. 

We are all mortal and one day we will die. The Bible teaches us that humans were intended to live with God forever, but because of our stubborn pride we rebelled against Him and are separated from Him physically (can't see Him) and spiritually (can't know Him).  When Jesus came to Earth He provided the way for us to be reconciled to God. We need to recognize our own sin and separation from God, realize that Jesus provided the way to deal with our sin by dying on the cross, and put our trust in Him.  If we do this Jesus says that after we die we will live again with Him.  That's the Christian hope.

In essence, hope is the ultimate reason for believing.