It's funny to me that while William Wilberforce needed to argue in his book, A Practical View of Christianity, that the religious affections--love, gratitude, joy, hope, trust, etc.--are a necessary a part of our relationship with and service to God, we have the very opposite problem only a couple of centuries later.  Today, knowledge about God, not emotion, is looked on with suspicion.  Many postmodern Christians prefer a fuzzy image of a God who is beyond our understandable categories, and they resist definitions that might "limit" Him.

But Wilberforce's words, though they were written to argue for emotion (i.e., the experience that postmoderns seek), also reveal the absolute necessity of knowledge as the foundation of true experience:

To ascertain [the genuineness and strength of the religious affections in a person] we must examine whether they appear to be grounded in knowledge, to have their root in strong and just conceptions of the great and manifold excellences of their object, or to be ignorant, unmeaning, or vague. . . .

Religious affections are only sustainable if they are attached to a real God who is known to be worthy of those affections; they simply can't carry themselves for very long.  But when knowledge is in its proper place, and the perfect and beautiful, solid and known truths about Him are meditated upon, desire for God inevitably follows; and that desire, in turn, fuels more intellectual pursuit of the truths of God.

Wilberforce charges that we all know this interplay between knowledge and affections exists, and it's the way any person would encourage another to continue on in a difficult task of any kind (not just religious): 

Weigh well (he would say) the value of the object for which you are about to contend, and contemplate and study its various excellences, till your whole soul be on fire for its acquisition. . . . Accustom yourself to look first to the dreadful consequences of failure; then fix your eye on the glorious prize which is before you; and when your strength begins to fail, and your spirits are well nigh exhausted, let the animating view rekindle your resolution, and call forth in renewed vigor the fainting energies of your soul.

Why, Wilberforce argues, should this be different only in the case of religion?  Knowledge is the root of love, passion, service, and perseverance.  With knowledge, you get all of these things.  Without knowledge, you'll have none of them.