The comet of 1812 symbolizes the growth of Pierre’s soul in unselfish love, though it takes Pierre a while to understand this. Pierre sees the comet for the first time after consoling Natasha (who’s distraught over her broken engagement) and acknowledging his love for her. Though he’s not free to marry her, Pierre feels something new being awakened in his soul. He comes to believe that, somehow, the comet signifies that he’ll be liberated from his idle, worthless Moscow life by the war of 1812—that his fate is mysteriously bound up with both Natasha’s and Napoleon’s. While his prediction isn’t completely wrong, his involvement with Napoleon is as a suffering war prisoner—not a triumphant assassin, as he’d hoped. After his ordeal, his soul has matured to a point that he can love Natasha freely.
The timeline below shows where the symbol Comet appears in War and Peace. The colored dots and icons indicate which themes are associated with that appearance.
Volume 2, Part 5: Chapters 18–22
Volume 3, Part 1: Chapters 19–23
...in the events surrounding Napoleon. He feels that all these events—his love for Natasha, the comet, the war—will somehow connect in such a way that he’ll be liberated from his worthless... (full context)
Volume 3, Part 3: Chapters 27–29