From the text:
"'You two [Joshua and Biff] are the ninnies here. You both rail on them about their intelligence, when that doesn't have anything to do with why they're here. Have either one of you heard them preach? I have. Peter can heal the sick now. I've seen it. I've seen James make the lame walk. Faith isn't an act of intelligence. It's an act of imagination. Every time you give them a new metaphor for the kingdom they see the metaphor, a mustard seed, a field, a garden, a vineyard, it's like pointing something out to a cat—the cat looks at your finger, not at what you're pointing at. They don't need to understand it, they only need to believe, and they do. They imagine the kingdom as they need it to be, they don't need to grasp it, it's there already, they can let it be. Imagination, not intellect'"
Lamb: The Gospel According to Biff