The control of the mind is not a problem peculiar to religious aspirants; people in all walks of life need to control their minds if they are to succeed in their respective vocation. No fundamental work for the uplift of the individual or of the community can ever be done without the mind being controlled. This book, which sets forth the teachings of Vedanta and Yoga on the nature of the mind and ways of controlling it, is meant for one and all.
The whole universe is one. There is only one Self in the universe, only One Existence, and that One Existence, when it passes through the forms of time, space, causation, is called by different names, buddhi, fine matter, gross matter, all mental and physical forms. Everything in the universe is that One, appearing in various forms. When a little part of it comes, as it were, into this network of time, space and causation, it takes forms. Take off the network, and it is all one.
-Swami Vivekananda