The body is the prop for the soul. So why not let the body be propped by a wall or a block? 

•   The props also motivate one to stay longer in an asana, so that one evolves the asana and matures in on

•   The props can thus contribute to deeper observation and understanding of the intricacies of the posture as well as the mind.

•   Action is movement with intelligence. The world is filled with movement. What the world needs is more conscious movement, more action.

B.K.S. Iyengar