By the time of the Katha Upanishad, the metaphor of the horse, though slightly altered from the Rgvedic imagery, had become perfectly explicit: “Know the self to be the chariot’s master, and the body, the chariot itself; know the intellect to be the charioteer, and the mind, the reins. “The horses”, the Upanishad continues, “are the five senses which must be reined in by our intellect and higher mind, and ultimately the self”. The chariot, here, stands for the body or our external being.