Alister McGrath explains the concept of faith for the New Atheists:
As William James pointed out many years ago, religious faith is basically “faith in the existence of an unseen order of some kind in which the riddles of the natural order may be found and explained.” Faith is based on reason, yet not limited to the somewhat meagre truths that reason can actually prove.
So is this irrational, as the New Atheist orthodoxy declares? Christianity holds that faith is basically warranted belief. Faith goes beyond what is logically demonstrable, yet is nevertheless capable of rational motivation and foundation.
It is not a blind leap into the dark, but a joyful discovery of a bigger picture of things, of which we are part. It is complex and rich idea, which goes far beyond simply asserting or holding that certain things are true.