This faith is a movement of the heart. This faith grasps that which cannot be seen. Saving faith grips the heart. It is something that cannot be seen. It is invisible, spiritual, divine in its origin.
Faith means that a new life has been planted in the soul.
Thomas Adams, a preacher from yesteryear said this well. It is not the quantity of your faith that will save you. So it is not the measure of your faith that saves you. It is the blood that it grips to that saves you. As the weak hand of a child, that leads the spoon to the mouth, will feed as well as the strong arm of a man, it is not the hand that feeds you, but the meat.