The basic lesson of The Wisdom of the Overself is that space, which provides a stage for things, time, which provides an order for events, and matter, which supplies the stuff of both, are all three really experiences of the mind, inseparable from the mind, constructed out of the mind, and nothing else. In other words, Mind is the essence of all existence, all life, all form, and this Mind is non-material. Pure Mind is nothing other than God and its reflection in the individual is nothing other than the divine soul. The book is admittedly difficult--mostly because of its metaphysical character and its compulsion on the reader to do much close thinking. However, it would be enough, after the first general reading, to reread only those portions which are the easiest to understand or which make the most appeal. The ground it covers can be only gradually trodden. In any case, it was written mainly to reach those who want to work their way up from the scientific standpoint to the spiritual one.
-- Notebooks Category 12: Reflections > Chapter 5: The Literary Work > # 215