what does simon seem to know when he tells Ralph that he will get back all right in chapter 7

Simon has faith that the boys will be rescued and is reassuring Ralph.

“You’ll get back to where you came from.” Simon nodded as he spoke.

He was kneeling on one knee, looking down from a higher rock which he held with both hands; his other leg stretched down to Ralph’s level.

Ralph was puzzled and searched Simon’s face for a clue.

“It’s so big, I mean—”

Simon nodded. “All the same. You’ll get back all right. I think so, anyway.”

Some of the strain had gone from Ralph’s body. He glanced at the sea and then smiled bitterly at Simon.