Using this simplest of definitions for faith as it has been written and explained by the author of the book of Hebrews I have underlined the three key words of this passage. Oftentimes faith and hope are used by believers synonymously and interchangeably. Hope in my opinion is the best word to define what faith is because Christians have a hope that one day they will be granted eternal life and be able to live in the presence of their god. The scriptures describe this afterlife as a time of bliss and eternal joy where there wont be any pain and sorrow or the many struggles and strife that one endures in this present life.
One of the things I find most irritating is when theists assume that I don't understand the concept of faith. They often forget that I myself was once a theist and quite frankly, when you really think about it it's not so otherworldly that it could not be understood with a little bit of reading comprehension. Faith as used in a Christian context is hope in the promises of God as outlined in the Bible and the confidence and assurance that he will fulfill his promises to those that are faithful. See, now that wasn't so hard. Hope requires that you believe that God exists and that he will fulfill each and every last one of his promises.
6And without faith it is impossible to please God, because anyone who comes to him must believe that he exists and that he rewards those who earnestly seek him. Hebrews 11:6
Faith is believing in the unseen without evidence but rather entirely on a divine promise.
13All these people were still living by faith when they died. They did not receive the things promised; they only saw them and welcomed them from a distance, admitting that they were foreigners and strangers on earth. 16Instead, they were longing for a better country—a heavenly one. Therefore God is not ashamed to be called their God, for he has prepared a city for them. Hebrews 11:13;16
With this in mind let's move on to two examples from the gospels where Jesus in one instance chastised someone for not believing in the promise of his rising from the dead and in another where he sent someone as proof of God's power.
After the resurrection of Jesus one of his disciples Thomas was told by the others that they had seen him at a time when Thomas himself was not present. Thomas's response is famous for it demonstrates the mentality of a rational person and a skeptic.
So the other disciples told him, "We have seen the Lord!" But he said to them, "Unless I see the nail marks in his hands and put my finger where the nails were, and put my hand into his side, I will not believe." John 20:25
Later on we read that the apostle Thomas was granted his request, but at the same time he was chastised for his unbelief!
29Then Jesus told him, “Because you have seen me, you have believed; blessed are those who have not seen and yet have believed.” John 20:29
The portion of that verse that I have underlined is the actual working definition of faith and according to Christianity is absolutely necessary in order for one to obtain salvation through Christ. You must believe without having seen or requiring evidence! On this one occasion Thomas was granted the opportunity to validate his lack of faith with the evidence he asked and required of Christ.
In Mark chapter 5:1-20 we are told the tale of a man possessed by a legion of demons. He is said to live in the tombs and to be so strong as to be unable to be subdued by any man or other form of restraints such as chains. Once Jesus delivers this man from his demonic possession he then request of the Lord to go with him. But Jesus refuses to let him go and instead gives him the following instructions:
19Jesus did not let him, but said, “Go home to your own people and tell them how much the Lord has done for you, and how he has had mercy on you.” 20So the man went away and began to tell in the Decapolis how much Jesus had done for him. And all the people were amazed. Mark 5:19-20
Instead Jesus told the man to go and be a living witness to the power of God. He specifically sends him to his own people because they obviously knew of this mans history and his former condition. As in the story of Thomas in this case faith was not gained from not seeing but rather the seeing actually engendered faith. Contrary to believing without seeing faith came in both instances because of what was seen! This is just another one of those biblical contradictions that are not so obvious unless you know the scriptures. Jesus contradicts the biblical definition of faith through his actions in both the former and latter case.
So my question to theists today is if he could do this back then, then why can't he do this today? If he truly wanted us all to be saved I would hope that he would do everything in his power to help us who don't believe to believe. This was the request of a man whose son was possessed by a demon in Mark chapter 9.
23“ ‘If you can’?” said Jesus. “Everything is possible for one who believes.”
24Immediately the boy’s father exclaimed, “I do believe; help me overcome my unbelief!” Mark 9:23-24
So apparently it's not too much to ask the Lord to help or give me a reason to believe. I too have made a similar request to that of the apostle Thomas when I left the faith in 94' and the Lord has yet to answer my last prayer request. I guess I just wasn't meant to be saved! The decision to worship god in this life is a life changing decision that in my opinion requires careful thought and evidence. To date no Christian rationalizations in the defense of faith without seeing has satisfied me. This is the main reason why I live under the belief that God does not exist just as I do with similar beliefs such as bigfoot, fairies, elves, unicorns, etc. Theist, the burden of proof is entirely on you to demonstrate to us doubters and unbelievers that your God exists. Otherwise, the rational choice is to assume that he doesn't.
Note: All biblical texts are taken from the New International Version of the scriptures.