In Chapter 5, what is the paradox of the boys' attitude toward the beast?

Golding blends irony with paradox so effectively that it becomes difficult to distinguish one from the other. A paradox is a statement that appears to be contradictory or impossible but expresses a striking truth.  Irony—in this case structural—refers to an implication of a reversed meaning that we might not appreciate the irony until we finish reading the entire piece. It is paradoxical that something that doesn’t exist could frighten someone, because logic would suggest that we must be frightened about something. The greater truth here, however, is that people are frightened more about what they don’t know than what they do know, and it is this fear of the unknown that terrifies the children. Golding ultimately locates this fear inside the children, which we especially see when Simon encounters the Lord of the Flies. Piggy’s insistence that beasts don’t exist because if they did “things wouldn’t make sense…they wouldn’t work,” which is his way of dismissing the “unknown” turns out to be ironically true, for as “civilization” breaks down on the island things don’t make sense and tragic actions that are not intended occur.