To believe in something is to hope in it as well. But what if the things that we hope for or believe in are worthless? What if everything regarding our hopes and beliefs are in this world only, and not in faith in God. No belief system that man has in place of the Gospel can guarantee anyone redemption or resurrection. Worldly and carnal belief systems are therefore in vain; they do not or cannot promise eternal life.
Christians look forward to a life with God in heaven, which comes after this life; unbelievable to some, but true. We are not hopeless, but hopeful. In Ephesians 1, Paul tells us that we have been accepted in the beloved. This epistle affirms our life in Christ after we are no longer in these mortal bodies. God's promise and warning to us in John 3:36 is that "he who believes in the Son hath eternal life; and he who does not believe the Son shall not see life, but the wrath of God abides on him."