The dread of evil is a much more forcible principle of human actions than the prospect of good.
Though he once said breathing is boring, Sherlock never would have considered stopping. Life was too full of fascinating puzzles.
He never imagined that he would find something or someone worth dying for until he met John. Even then, it never crossed his mind until Moriarty made it clear that he was willing to do anything to win.
Sherlock had never known true fear until that night at the pool. If the bomb exploded, both of them would die, but it never crossed his mind to leave without John. His own danger was a mere footnote to the terror he felt for John's life.
So there was no question that he had to jump. Of course, he did his best to find another way out, but when it came down to it, when it was John's life or his, there really was no contest.
"That's what people do, don't they...?"
A/N: John Locke (29 August 1632 – 28 October 1704) was an English philosopher and physician. He had a great influence on much of history, including the US Declaration of Independence.