Symbolism, Imagery, Allegory
In the middle of the book, Pierre starts fooling around with numbers and codes and ciphers, Freemason-style, and eventually drives himself crazy enough to believe that his name and Napoleon's name both add up to 666, marking both of them as "the Beast" from the Book of Revelation. Pierre takes all of this insanity one step further and concludes that Napoleon is the anti-Christ, and that he, Pierre, is the anti-anti-Christ, who needs to assassinate Napoleon.
Why this convoluted nonsense? We'll throw out a few suggestions. First, it could be a comment on the whole discussion of free will versus determinist and fate that is Tolstoy's number one issue – and a way to show that determinism from a global, universal perspective (what Tolstoy advocates) is not something individuals could actually figure out themselves, since on a human level, we experience the determinism as free will. Or, second, it could be yet another of the whole series of fixed and inflexible ideas that the book's characters obsess over (and a way of thinking that Tolstoy totally hates). What do you think?