I have a theory that we lose some of our spiritual vigor and urgency--especially some of us who are clergy and/or religious--because we have (perhaps unreflectively) bought into a certain secular philosophy of religion. And what's worse, it's one that makes us into subtle agnostics and pelagians.
The theory goes like this: religion is a category of human life and expression, and each particular religion is a path, but all the paths are going to the same place. Call this goal of religion what you will: "God," "the transcendent," "spirituality," what have you.
This imagination has certain secular advantages: it precludes the idea of competing religious claims, relieving us from intolerant religious violence. It means that "people of faith" can work together toward common goals of compassion and justice without the nagging feeling that they are relativizing their particular beliefs.
But there is a dark side; a price to pay for this relativism.
First of all, the theory contains the assertion that there is genus called "religion" into which all kinds of different phenomena have to be stuffed. This sounds fine when you're filling out a form and have to fill in the blank that says 'religion,' but it breaks down quickly in the particulars. A Christian and a Jew are hardly two species of the one genus "religion." More accurately we have to say that the Christian is a particular kind of Jew, or that both are the fraternal twins born of the end of Second Temple Judaism. Problems increase even more when we try to go outside of the Abrahamic heritage.
Second, the theory suggests that nobody really knows God. We are all using these different cultural and linguistic constructs that we call "religions" to try to articulate something about God, but the very fact of their diversity demands that God is some kind of Kantian noumenon to which nobody has any kind of genuine access. This is why, if we make the relativistic philosophy of religions our framework, we have become agnostics, who don't really know how to say anything for sure about God. And agnostics don't die for their beliefs. And they don't live for others for God's sake either.
Third, this religious relativism makes us into pelagians, because religion is about our human expression of an experience, our human articulation of whatever it is the different faiths are aimed at. This is, in fact, the opposite of Christianity, which proclaims that the gap between the human and divine has been bridged, not by human effort or cultural or language, but by God himself in the humanity of Christ.