In the Metal Gear series, there are themes in most of the canonical Metal Gear games. These themes play an important part in the game's story. Metal Gear creator Hideo Kojima has said that the themes are messages that can be passed on to the next generation. By the end of the game, the themes lead to a conclusion. The Metal Gear Solid 3: Snake Eater official guide by Piggyback speculated that the games overall story carry several implicit parallels to Nietzschean philosophy, specifically Friedrich Nietzsche's "The Eternal Return of the Same."