Max Heindel 
An Elementary Treatise Upon Man’s Past Evolution, Present Constitution And Future Development [EPUB ebook] 

This book is written by Max Heindel, the founder, and Messenger of The Rosicrucian Fellowship. This is a reference book of the Fellowship students and Probationers. This book is also referred as Cosmo-Conception or Mystic Christianity.
The founder of the Christian Religion stated an occult maxim when He said: ‘Whosoever shall not receive the kingdom of God as a little child shall not enter therein’ (Mark 10:15). All occultists recognize the far-reaching importance of this teaching of Christ and endeavor to ‘live’ it day by day.
When a new philosophy is presented to the world it is met in different ways by different people.
One person will grasp with avidity any new philosophical effort in an endeavor to ascertain how far it supports his own ideas. To such an one the philosophy itself is of minor importance. Its prime value will be its vindication of HIS ideas. If the work comes up to expectation in that respect, he will enthusiastically adopt it and cling to it with a most unreasoning partisanship; if not, he will probably lay the book down in disgust and disappointment, feeling as if the author had done him an injury.
Another adopts an attitude of skepticism as soon as he discovers that it contains something which HE has not previously read, heard, or originated in his own thought. He would probably resent as extremely unjustified the accusation that his mental attitude is the acme of self- satisfaction and intolerance; such is nevertheless the case; and thus he shuts his mind to any truth which may possibly be hidden in that which he off-hand rejects.
Both these classes stand in their own light. ‘Set’ ideas render them impervious to rays of truth. ‘A little child’ is the very opposite of its elders in that respect. It is not imbued with an overwhelming sense of superior knowledge, nor does it feel compelled to look wise or to hide its 
nescience of any subject by a smile or a sneer. It is frankly ignorant, unfettered by preconceived opinions and therefore eminently teachable. It takes everything with that beautiful attitude of trust which we have designated ‘child-like faith, ‘ wherein there is not the shadow of a doubt. There the child holds the teaching it receives until proven or disproven.
In all occult schools the pupil is first taught to forget all else when a new teaching is being given, to allow neither preference nor prejudice to govern, but to keep the mind in a state of calm, dignified waiting. As skepticism will blind us to truth in the most effective manner, so this calm, trustful attitude of the mind will allow the intuition, or ‘teaching from within, ‘ to become aware of the truth contained in the proposition. That is the only way to cultivate an absolutely certain perception of truth.
The pupil is not required to believe off-hand that a given object which he has observed to be white, is really black, when such a statement is made to him; but he must cultivate an attitude of mind which ‘believeth all things’ as possible. That will allow him to put by for the time being even what are generally considered ‘established facts, ‘ and investigate if perchance there be another viewpoint hitherto unobserved by him whence the object referred to would appear black. Indeed, he would not allow himself to look upon anything as ‘an established fact, ‘ for he realizes thoroughly the importance of keeping his mind in the fluidal state of adaptability which characterizes the little child. He realizes in every fiber of his being that ‘now we see through a glass, darkly, ‘ and Ajax-like he is ever on the alert, yearning for ‘Light, more Light.’
The enormous advantage of such an attitude of mind when investigating any given subject, object or idea must be apparent.