The Yogis say that that part of the human energy which is expressed as sex energy, in sexual thought, when checked and controlled, easily becomes changed into Ojas, and as the Muladhara guides these, the Yogi pays particular attention to that centre. He tries to take up all his sexual energy and convert it into Ojas. It is only the chaste man or woman who can make the Ojas rise and store it in the brain; that is why chastity has always been considered the highest virtue. A man feels that if he is unchaste, spirituality goes away, he loses mental vigour and moral stamina. That is why in all the religious orders in the world which have produced spiritual giants you will always find absolute chastity insisted upon. That is why the monks came into existence, giving up marriage. There must be perfect chastity in thought, word, and deed; without it the practice of Raja-Yoga is dangerous, and may lead to insanity. If people practice Raja-Yoga and at the same time lead an impure life, how can they expect to become Yogis?