What is faith?

After questioning the rationality of those believing in Mohammed and in the Koran, it occurred to me that I should address this issue. Really, I will get back to reading the book and responding to it. I may even share some verses that encourage me (the way they were meant to, and that we can all be in agreement on.)
The Bible says faith is the substance of things hoped for, the evidence of things unseen. It points out that one doesn't hope for what he already possesses. So I do grasp that to some degree belief is based on, well, believing in something.
I suppose it is true that "the hour I first believed" it was based on an emotinal response to the message of hope and forgiveness. Hope that I could know God and go to heaven. Forgiveness enabled me to be freed from the burden of guilt and shame. (Though as a sixteen year old I hadn't done a whole lot-my mind was aware of uncleanness, emptiness, and imperfection.)
I have to say, as for as some objectivity, I had had a dream in which God came to me, and told me I was now dead to the world, that He loved me and wanted me to be with Him. Not so much that He wanted me dead, but that His claims on my life left me not free to do whatever I wanted. I had had friends who had told me about Jesus whom I had disregarded.
I only went to the meeting to prove that I was gospel proof, that I was above that sort of thing, to get them off my back. So I was not seeking some emotional release, nor was I trying to lay aside my mind. That night and for the next week, I analyzed what I had done, trying to decide whether I wanted to pursue the commitment made emotionally or whether to disregard it. But the peace of God is hard to disregard, and His love is overwhelming. I could not turn away from that to return to emptiness.

And there is a time when knowing that one knows something is valid. One knows he is in love. Not something easily proven to others, though others can see when a life is transformed. In that manner, I knew that I had encountered God. I wasn't just believing or hoping some Being existed. I had spoken to Him and He had spoken back.

A year or so later, I read discussions about how Chrisitianity is based on historical facts. Neither the Jews nor Romans could find Jesus'body though it was in their interests to do so. The apostles turned from being men of cowardice and expedience to become brave witnesses of something so powerful they could gladly risk their lives, leaving all, to tell the world the gospel. And as repeated before, the 500 witnesses who had seen a resurrected Christ also enlisted in this endeavor, to tell others what they'd seen.
The topping on the cake was the testimony of Paul, that that fact mattered. If the dead were not raised, then, he told us,we are still in our sins-having not been forgiven. And we are of all men most to be pitied.
He does not endorse the modern notion that everybody has to believe in something. (To them it really doesn't matter if it is true, if it makes others feel good and gives them courage to face life.) Several times in his letters Paul discusses all the things he has endured for the ministry. Being beaten and left for dead, whipped, jailed, surviving a shipwreck, and so forth.
He says he has learned "in whatever state I am to be content: I know how to to be abased, and I know how to abound. Everywhere and in all things I have learned both to be full and to be hungry, both to abound and to suffer need. I can do all things in Christ Jesus. Keep in mind this was a member of the elite. Not merely Roman, but Jewish. He was a disciple of Galaliel. Close associate of the high priests-having been given permission to go into other places to pursue Christians, to put them to death. He was born a Roman citizen. He gave up all that prestige, comfort, and security. In exchange for losing intellectual associates, he received for himself being persecuted, poverty, and a virtual nomadic life. Travelling all over the world, he made tents to support himself.
But he would not be stupid enough to submit to this if it were not true.
He had after all, had the opportunity of interviewing some of those 500 witnesses: Peter, and Jesus' brother James, and many of the church in Jerusalem. (This in addition to the personal vision and appearing of Jesus to him.) His choice would be life is too valuable. If it is not true, make yourself comfortable. "Let us eat and drink for tomorrow we die." In another place he states he has the right to have a wife, though he does not. I assume he would not mention this if he did not at times feel the loss of this.
In Philippian chapter 3, he states he has suffered the loss of all things "that I may gain Christ.... That I may know Him and the power of His resurrection, and the fellowship of His sufferings...if by any means I may attain to the resurrection of the dead."
Years later, I endured facing life as well as the costs of believing in Jesus. There were definite times when giving up would have been desirable, certainly less costly in many areas. However, I had to say along with Peter, "Lord to whom can I go? Only You have the words to eternal life." And I still say that, even after reading the Koran and hearing the signs of Mohammed. After all, an apostle who tells his own wife-Khadijah, and his daughter Fatima (according to your hadith) that he cannot guarantee them entrance into heaven, has an empty message. He is powerless to help anyone.
It is air. A faith in which one can only say "I hope that I am" is a waste of effort. It may make for a better psychological experience giving one hope that things will work out all right. But a faith based on air is dangerous.
Air can be magnificient. I can get on an airplane and travel across the world, knowing the physics of air travel is based on fact. Or it can be fatal. I can step off a cliff and it will not hold me. The only times one does not fall from a tall building when separated from a physical support is in the cartoons.
Now I suppose a believer could throw a fit should someone tell him the substance of his faith is air. Yelling and screaming, kicking or stomping, he could defend his belief in his security to step out. But the proof of his faith is not in the depth of his emotion. The proof is whether his faith is stronger than gravity.
If it is not based on fact, no matter how deeply he has devoted himself to it, his faith has failed him. Furthermore, those who taught it to him have failed him too, as well as having deceived their own selves. And someone needs to reach the point where they are willing to shout "stop! Stop this endless procession of well-meaning obeyers from throwing their lives away, submitting to error. Please find something true, and strong enough to hold you."
So I beg you, examine your faith. Not the depth of it, the emotion and devotion to the Prophet. I assume you have the emotional intensity or you would not be reading about this subject. But examine the factual basis. Are you walking on air, waiting for the realization that will start your plunge?
Instead of one who tells his family he cannot help, better to believe in One who promises a total stranger-the thief on the cross who asked for His mercy-"today you SHALL be with me in paradise." Believe in someone with the authority to give salvation.