THE CALL FOR HELP

We know the numbers (4, 8, 15, 16, 23, 42) were representations of Jacob's candidates who were to be the next island guardian. But as the series started to wind down, and the numbers were being clarified to the viewers, there was one strange twist that is often overlooked by us.

When Hurley and Jack were sent to the lighthouse, Jacob told Hurley to set the lighthouse dial to 108. 

The dial read:
108 - Wallace 

This person whose name was also written on the cave wall.  But angry Jack smashed the mirrors before Hurley could set the dial to 108. Jack smashed the lighthouse mirrors because he saw that it was a machine that spied on him throughout his life. He was angry that he had been secretly chosen to crash land on this island. It was through the lighthouse that Jacob found his candidates and brought them to the island.

This scene opens the possibility that Jacob had "given up" on the current castaways as his successor. He may have needed the lighthouse mirrors to project his image or spirit into the real world to contact "or touch" Wallace and bring him/her back to the island.

But since Jack broke the lighthouse, Jacob could not call another wave a cavalry candidates to his aid. He was stuck with the 815ers. That is why later on Jacob told Hurley that moping Jack "had to figure things out himself." That thing was an acknowledgement that at some point Jack would have to sacrifice himself for the benefit of his friends. There was miracle fix for his situation.

Who could this Wallace be?

Philosopher Robert Wallace is well known for his fascination with numerology, and had a famous connection to Hume, another famous philosopher whose name Desmond shares. Wallace may not be a specific person but it is likely at least a reference to the philosopher, as the show does like to give its characters the same names as famous philosophers (Hume, Rousseau, Locke, etc.)

Wallace, named after a economist, could have been The Economist that Sayid assassinated on the golf course.  Sayid was told that there were men who killed worked for Widmore and who were involved in Nadia's death.  Then the name would  have been scratched off before Hurley was to set the lighthouse (unless it was going to show Sayid's action to warn Jack that Sayid was now evil.)

It is more likely that it was a new candidate which never made it to the island. Someone that Jacob needed to call and bring to the island because he was running out of viable candidates to defeat MIB. It was possible that since Jacob's demise, he could no longer operate the lighthouse in the flesh, so he needed Jack or Hurley to call the new candidate to the island.

The call for reinforcements would show that whatever was happening on the island, Jacob feared that he was losing control of the situation. Though we are never told the actual outcome of MIB leaving the island, we are led to believe that the consequences would be dire to all mankind.

Or Wallace could have been a clue to premise of the series.

The novel, A Wrinkle in Time, was seen on the program. Charles Wallace was a character in that series of children's books. He was a psychic child in stories about time/space travel, changing the past, series of "might-have-been" events, turning point events battles between the powers of good and evil, a large evil cloud called The Black Thing (in the movie, The Darkness) and an evil intelligence called IT who controls people's minds.

These are the same themes running through the LOST saga. Walt was a psychic child who longed to change his past. The Black Thing is the smoke monster. An evil intelligence (Dharma, Ben, Jacob) controlled or manipulated characters' minds. The white and dark stones were supposed to symbolize some conflict between Jacob and MIB.