To illustrate the limits of reason, Rabbi David Wolpe, author of the new atheism-busting book, Why Faith Matters, offers this parable — “Buridan’s ass.” Jean Buridan (1300-1358) was a French Priest who told this story:

Imagine a donkey equidistant between two barrels of hay. Now imagine that this donkey is a rationalist, someone who will do nothing if it is not in accord with the dictates of reason. He cannot reason why one mound of hay is superior to the other. He stays in the middle trying to decide which should be his supper. Since there is no reason to move to one or the other, in time, the donkey starves to death.

The parable, according to Wolpe, shows that “reason bleached of value starves us.” Apparently, neurologists have demonstrated that “when people who suffer brain injuries that destroys their capacity to feel seek to make decisions, their decisions are disastrous.”
In other words, faith and emotion make reason work better. More of Wolpe doing battle with Richard Dawkins, Sam Harris etc. here.