That is an important question. Lets begin with a definition of terms. Faith might be defined as committment to a belief in the absence of concrete evidence. Although it is often associated with spiritual committment, faith is something we exercise in varying degrees in everything we do. Considering an example may help illustrate what faith entails.
I was at one time an accomplished rock climber. When rock climbers are on the outcrop, the lead climber moves up to a stopping point, then sets protection and "belays" or protects the partner as he or she climbs, by keeping just the right amount of tension on the rope connecting the two. If the second climber should slip, the lead climber is responsible for stopping the fall. But often they are out of sight of one another, and the second climber cannot see where his or her protection lies. In this case, it would not be possible to move without faith. As I am following a lead climber, I must believe that he is not asleep on the job, and that he is ready to catch me if I slip. I must further believe that the rope is strong enough to stop my fall. If I believe these things, I can climb routes that would otherwise seem to be impossible. That is an example of faith. It is not faith in God, it is not religious faith in the normal sense of the word, but it is faith, and your life may depend upon it. That is why when you are climbing, you want to know the person you are linked up with. Religious faith is like that. I want to exercise faith in Someone, I have through experience and study, come to know as reliable and benevolent, Someone who will not let me perish when I slip on the dangerous routes of life.
The book of Hebrews in the New Testament contains a chapter dealing with faith. In that chapter (Hebrews 12), the author states in verse 3: "By faith we understand that the worlds were framed by the Word of God, so that the things which are seen were not made of things which are visible." So at the very beginning of faith is belief in origins. We cannot correctly understand the origin of the earth or life on the earth without exercising faith. This should come as no surprise. How can we know with certainty where we came from, unless a reliable witness tells us? We were not there to observe, and neither were any of our contemporaries. So no matter how certain a person may be about issues of origins, faith in something is always required. The essential question is: Will I place my faith in the account of an eyewitness, or will I place my faith in human reason? Human reason may be guided by all sorts of motives that are rarely visible to the observer. The well known philosopher Aldous Huxley, son of Darwin's chief protagonist, Thomas Huxley, was very blunt in his book Ends and Means (Harper Bros., 1937. p312, 317-18):
Where the issue of origins is concerned, faith will always be required. You may choose to follow the crowds, those who choose to have a Creator-less world because it is convenient, or you can choose to follow the Creator God, who has revealed in His word, not only that He created, but how He performed the process.
2010 Arthur V. Chadwick, Ph.D.