The words "thoughtful" and "thoughtless" signify a rhythmic or unrhythmic state of mind, and balance, which is the only upholding power in life, is kept by rhythm. Respiration which keeps mind and body connected, and which links the mind and soul, consists in keeping rhythm every moment when awake or asleep; inhaling and exhaling may be likened to the moving and swinging of the pendulum of a clock. As all strength and energy is maintained by breath, and as breath is the sign of life and its nature is to flow alternatively on the right and left side, all this proves rhythm to be of the greatest significance.