Simon told the other boys at a meeting that perhaps there was a beast and that the beast was just themselves. This indicates that Simon does not believe that the beast is a creature with wings, claws and teeth but that it is simply the boys themselves. The beast is just the desire and capacity to do evil which is within us all. Later in the book, after Samneric report actually seeing the beast, I quote... "However Simon thought of the beast, there rose before his inward sight the picture of a human at once heroic and sick."
No, Jack did not believe that Simon was the beast in "Lord of the Flies." He mistook Simon for the beast during a frenzied dance in the forest, but later realized his mistake and Simon's true identity.
He knows that the beast is inside of them. In other words that the beast they believe is out there is actually the evil inside of them.
Simon's comment was about the beast. He suspected that the beast was not an animal and obviously didn't believe that it was a ghost. This left only one remaining possibility, that there was no beast. Simon believed that the beast was simply a product of the boy's own imaginations. The beast only existed in their own minds. However there was a deeper reasoning to Simon's comment. Simone suspected that the beast wasn't just a product of the boys' own imaginations but was actually the boys themselves. It was the boys themselves who were the 'beast,' capable of hurting, of killing and of committing acts of evil.
Simon
Simon was mistaken for the beast in "Lord of the Flies". He was killed by the other boys during a frenzied tribal dance on the beach.
Simon.
SIMON.
Simon is the only character who realizes that the beast doesn't exist and that the true beast is within themselves.
The boys mistake Simon for the beast in a frenzy and end up killing him in their primal and frenzied state.
Simon concluded that the beast was harmless and horrible. However, he was unable to effectively communicate this to the others, and instead, Piggy began to tell everyone about Simon's belief regarding the beast.
From the book, "The Lord of the Flies", Simon pictures the new beast as the evil that is inside of everyone. He sees this human as once heroic and sick.
The beast tells Simon that it is a part of him, and that it suggests that it is within every human on the island, foreshadowing the idea that the true threat lies within themselves and their own actions.