I would contend that faith is a natural part of humanity, but not it's foundation; nearly all cultures exercise some form of faith based spiritual practice (faith being defined as belief in things which can not be proven, or in philosophical terms; mythos in action). Since most human civilizations have developed faith, without direct contact with other faith oriented traditions, I think it would be fair to assume that faith is core to the human experience. Whether or not each of us takes humanity on faith (or even believes in such a concept as humanity) is primarily up to us to decide. Personally I think that there's a great deal to be said for having faith in humanity without demanding proof. But, as philosophers we probably ought to try to go beyond the faith argument, and search for some deeper explanation of what it means to be human, founded in logic and emotion.