Blake shows how youth can be unaware that they have been corrupted. When they are brought down a path of ignorance, they become trapped in the dark, unless a light appears to guide them. Youth have few doubts, and when that is fed into, they continue without doubts, content with not having opposing views and nuance - stuck in their own folly.

Doubt is fled seems very much like a point on the youths lack of internal questioning. They do not think there is room for doubt, as they must be right - a point made from their lack of understanding the nuance of truth and reality.