This book serves as an introduction to the six systems of Hindu philosophy. Though these six systems are different in their approaches to the truth, they are unanimous as far as the final goal of humankind is concerned, which is, total eradication of suffering and attainment of state of eternal peace.
Those who have succeeded in attaching or detaching their minds at will have succeeded in Pratyahara, which means gathering towards, checking the outgoing powers of the mind, freeing it from the thralldom of the senses. When we can do this, we shall really possess character; then alone we shall have taken a long step towards freedom. Before that, we are mere machines.
-Swami Vivekananda