In this chapter, we learn that the plan was for the two of them to fight and kill each other. In fact, from the moment they met, the two men planned to use each other for their own ends. Now that they've seen each other, it's clear that the two have become enemies. In order to stop them from destroying each other's lives, they'll have to give each other half of the other man's notebook. In other words, if they both die, then either of them will get to keep the rest of his master's papers. This is the plan that was originally devised for them to keep each other alive while he created a new world. But now that he's seen what's going on, he realizes that he can't keep them both alive.