A metaphor for preaching the dharma, that is, spreading Buddhist teachings. The Buddha's dharma is often called a "vehicle" (jō 乘, S. yāna), and to turn the wheels of a vehicle is to propel it forward. In Indian mythology, a "wheel-turning king" (tenrin ō 轉輪王, rinnō 輪王, S. cakravarti-rāja, cakravartin) is a mighty emperor or world ruler; the expression derived, perhaps, from the image of a king's chariots - his wheels - conquering a vast area. In the life story of the Buddha Shakamuni, a sage predicts before his birth that if he remains in the world he will become a wheel-turning king, but if he chooses the path of an ascetic renouncer he will become a spiritual conqueror instead: the Buddha, who after his awakening begins to preach and thus turns the wheel of dharma. →"dharma wheel."