The tale of The Little Engine that Could remains a perennial classic of early children's literature, and understandably so. The story (which we all know, so why am I bothering to repeat it?) involves a little blue engine commissioned with the task of pulling a large train over a very large hill. Initially success appears impossible as the little engine begins chugging up the steep grade, all the while repeating the determined mantra "I think I can, I think I can". Then success appears improbable as he rises higher up the hill, still chanting his hope. Then success appears not likely as he rises higher still. And then he crests the hill, and "I think I can" morphs into a triumphant "I know I can!" And with that he picks up increasing speed, as children the world over clap their hands in delight and warm fuzzy feelings abound.
The morale of the tale is clear. A positive can-do attitude can accomplish great results. And even if it doesn't guarantee you'll crest every hill, it makes it more likely.
. And so it is that the little train that believes it can scale a large mountain, will be more likely to find success because of his "I think I can" attitude.
But even so, there are no guarantees. And the little engine might very well meet a hill which he will not be able to scale. Wisdom dictates that he should find a balance. If he sets off to scale Pikes Peak, we might fold our hands and wait skeptically. If he attempts Mt. Everest we might call our friends over to watch the impending disaster.
Now we turn from children's lit to the methods of science, and in particular methodological naturalism. This is the principle that says when seeking to understand the natural world we ought to refrain from invoking non-intelligent causes. Like the little engine who says "I think I can" we must always chant "I think I understand". And eventually we will clear the crest of the hill, no matter how improbably high the mountain (ahem, note the clever Dawkins allusion).
But like the little engine that could,