He argued unconvincingly that they would let him alone, perhaps even make an outlaw of him. But then the fatal unreasoning knowledge came to him again. The breaking of the conch and the deaths of Piggy and Simon lay over the island like a vapor. These painted savages would go further and further. Then there was that indefinable connection between himself and Jack; who therefore would never let him alone; never.
What is meant by the phrase "fatal unreasoning knowledge" as used in the passage above?