The Fool trusts in life and expects his path to be a happy and rewarding one. There is faith in the gods to see him through and a complete absence of fear.
Sometimes the Fool is seen as too carefree - certainly a good dose of other people's more negative reality could damage him. However, for as long as the Fool has faith in his own purity and innocence, others will not be able to take advantage.
This is the child within. This is how we were before the many experiences of life forced us to build up so many walls. The Fool does not shade himself from the light - here we are born and from here we walk the path. It's time to jump off the cliff...