The popular meaning of fool is someone stupid, gullible, or laughable. But the Tarot Card definition is quite different.
The picture I've seen shows a boy, smiling honest, eyes uplifted towards the sun above, about to step off the edge of a cliff. I like this because it shows both the happiness and the let-downs that come from believing that the world is a good, honest place. Personally, I'll be a fool anyday--the other options are certainly no better.