This is not the result of any intellectual perception of the need nor of a resolve to develop the necessary changes, but of a desire, often though not always a mute, inarticulate and unthought desire. That desire attracts a force which satisfies it. We have a will beyond mind which dictates the change, we have a force beyond mind which effects it. The force is Prakriti or Shakti, the female principle in Nature which is at the root of all action. Behind both is the single Self of the universe which contains both Jiva and Prakriti, spirit and material energy.
Yoga is therefore no dream, no illusion of mystics.
It is known that we can alter the associations of mind and body temporarily and that the mind can alter the conditions of the body partially. Yoga asserts that these things can be done permanently and completely. For the body conquest of disease, pain and material obstructions, for the mind liberation from bondage to past experience and the heavier limitations of space and time, for the heart victory over sin and grief and fear, for the spirit unclouded bliss, strength and illumination, this is the gospel of Yoga, is the goal to which Hinduism points humanity.