This innate ch'i disposes over his physical and mental well-being, and is something different from the "acquired ch'i" which he breathes in after birth, or from the "ch'i derived from the essence of water and grain" which he takes in through eating and drinking.
人與生俱來一種神秘無形的「先天氣」，先天氣主宰人的身心，不同於出娘胎後，以口鼻呼吸的「後天氣」，及藉飲食攝取的「水谷精氣」。