I have thought long and hard on this topic.
I see a number of posts above quoting biblical scripture as a definition of faith - but isn't there a question of the authenticity of the scriptures in this context?
Example: The topic under discussion is "What is faith", but you have to have faith that the bible is truely the Word of God before you can quote it. If you are at a point (spiritually speaking) where your faith isn't total, how can you belive the bible has the answer?
a) IF you trust in the scriptures, the question of faith is merely the definition of a word - you already have faith, you just want to know what the word means.
b) IF your faith is truely in question, there really is nowhere to look in the physical world to find an answer. You can't look to the bible, because it may not be true - such is the case with any other writings from any other religion.
Faith is belief and trust in something (or someone) without physical proof. Therefore you can't look to the physical world to find it.
Jehovah's Witness was the ONLY religion I knew, and I have faith that it is false, but that is where my faith ends. I don't know IF there is a God, and IF there is, is it the God of the christians, hindus, bhudists, or any one of the housands of other religions worldwide. I don't know, and I could spend every waking moment studying every religion on Earth to find the answer, and still might never find out.
I had faith that what I was taught as a child was true - when I became an adult and questioned further (as anyone with a reasoning mind should do), I found their teachings and practices lacking - as most of us here have. On that day my "faith" was shaken to the core, not only could I not believe in the JW version of things, but anything remotely spiritual was under scrutiny, from the mundane, to the truely profound, and even the BIG question "Is there a God?" has me shrugging my shoulders.
All of this dialog does not go without a point though, and those of you who have bothered to read this far are in for a treat.
My experience of faith has given me two things,
1) I know what faith is, because I had it. Faith is believing with your entire being that God exists, that God cares, and that what He has written down for us is true. We have a purpose for being here and we will be rewarded for following the instuctions set forth by Him.
2) Faith is the base upon which all things spiritual is built. The human psyche is flexible and maleable, like clay. Knowledge molds the clay of your inner self to shape the person you are to become. Faith is the kiln that fires the clay to make a strong and firm vessel where your spiritual self will reside. And faith, like a clay pot, once broken is never the same, it can be put back together, but it will be forever cracked and weak. Some people with dilegence and perseverence may be able to rebuild their faith, others may not.
I think I am in the latter group, but fear not - I don't think I need faith to survive, I'm happier now than I have ever been, for you see, faith can be uplifting, but it can also be an unbearable yoke.