Yoga is a union of the organ systems in the body with the consciousness in the mind, aiming to bring about a state of equanimity (calmness). Philosophically, yoga produces a union of body, mind, and energy (or soul or spirit) to achieve a happy, balanced, and useful life. The ultimate aim of yoga is to reach kaivalya (emancipation or ultimate freedom), as defined by the Iyengar school of yoga.