When Ralph is hiding and stares straight into the savages' eyes in the novel "Lord of the Flies" by William Golding, he remembers what Simon told him about the "beast." Simon had told Ralph that the real "beast" is not something that exists externally, but rather it exists within each of them. Simon had said, "Maybe there is a beast… maybe it's only us."
Ralph remembers this because, in that moment, he sees the savage's eyes and realizes that they are not the eyes of an external beast, but the eyes of another human being, just like him. This realization makes him understand that the true evil on the island is not some external force, but rather the darkness within themselves that is driving them towards violence and destruction.