This book is Loosely based on the biblical proverb,"As a man thinketh in his heart, so is he,"
i.e. your action is nothing but the representation of your inner thought.
In introduction itself there is a beautiful poem, which is the real essence of the complete book, which says that Your Mind is the real power and all your "Joy' and 'Suffering' is only because of your thought". Many people believe that their thoughts are secret, but it is not. Whatever you are thinking will be known to the world in form of your action. Therefore all aspect of your life is under control of your thoughts.
It cautions you to control your thought. A portion of poem is : - Mind is the Master-Power ....... Man is Mind, ....
....... Brings forth a thousand joys, a thousand ills ....
....... He thinks in secret, and it comes to Pass ....