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.
Anything that is secret and mysterious in these systems of yoga should be at once rejected. The best guide in life is strength. In religion, as in all other matters, discard everything that weakens you, have nothing to do with it.
-Swami Vivekananda