During the past few years the most serious part of the author's study and reflection has been devoted to the subjects discussed in this book. These, briefly stated, are as follows: Firstly, that all mental or cerebral faculties can by direct scientific treatment be influenced to what would have once been regarded as miraculous action, and which is even yet very little known or considered. Secondly, in development of this theory, and as confirmed by much practical and personal experience, that the Will can by very easy processes of training, or by aid of Auto-Suggestion, be strengthened to any extent, and states of mind soon induced, which can be made by practice habitual. Thus, as a man can by means of opium produce sleep, so can he by a very simple experiment a few times repeated-an experiment which I clearly describe and which has been tested and verified beyond all denial-cause himself to remain during the following day in a perfectly calm or cheerful state of mind; and this condition may, by means of repetition and practice, be raised or varied to other states or conditions of a far more active or intelligent description. This treatise was first published under the title of "Have You a Strong Will?". It comes here with an Easy to Read Layout designed to make reading comfortable.