Here’s an interesting quote from William Walker Atkinson:

“Mind‑Power has been known to the race, in one form or another, from time before history was written. In the earliest records we find many traces of it among all peoples.

Many have been turned away from a serious consideration of the subject by the fact that many of its forms have been accompanied by the grossest superstition, and the most absurd repulsive ceremonies.

They have failed to see that underlying all the extravagant ideas and methods of application, there was to be found a fundamental law of Nature, as real and as constant as any other natural law or force. And, inasmuch as this law is in constant operation, and all are subject to its influence and effect, does it not become the duty of intelligent people to acquaint themselves with this mighty force or law, in order that they may understand its workings; take advantage of its benefits; and protect themselves against its misuse?

Believing that there is but one answer to this question, this book has been written in order to throw light on a subject commonly left in the dark, or at least in the twilight of the human understanding.

I am fully aware of the fact that many ingenious theories have been advanced by modern writers attempting to account for the phenomena of Mind‑Power. But all students of the subject are aware that these theories, cleverly as they have been designed, are more or less self‑contradictory, and many a reader has thrown aside the subject in disgust after a vain attempt at reconciling the opposing views.

And to make the matter worse, various cults and sects and “isms” have sprung into existence, the promulgators and leaders of which have used the accepted phenomena of Mind‑Power as a foundation upon which to build airy structures of religion, philosophy, and metaphysics.

Many of these cults have practically claimed a monopoly of the great natural force, and have assumed the right to be the sole custodians of the secrets thereof, alleging that they have the “only real article — all others are base imitators,” notwithstanding that all of them show that they have arrived at at least a working knowledge of the force, and are obtaining results — each obtaining about the same percentage of successes, notwithstanding the fact that each denies the other the fact of possessing the information and right to use it.

Is it not apparent to any intelligent observer that they are all using the same great natural force, in spite of their conflicting theories — and that their results are obtained in spite of their theories, rather than because of them?”