In being given the formal symbolic secrets the Candidate should reflect that he is receiving a first lesson in a long course of instruction of a private and occult nature; i.e., one not taught outside the Lodge, but hidden from public knowledge and intended to help him upon the path of his personal inner life. For having but just entered upon that path, it is proper that he should now be instructed how to tread it.
W L Wilmshurst, The Ceremony of Initiation, Part II
“Astral” Beings may thus be defined in the same way as “material objects”; they are the Unknown Causes of various observed effects. They may be of any order of existence. We give a physical form and name to a bell but not to its tone, though in each case we know nothing but our own impressions. But we record musical sounds by a special convention. We may therefore call a certain set of qualities “Ratziel”, or describe an impression as “Saturnian” without pretending to know what anything is in itself. All we need is to know how to cast a bell that will please our ears, or how to evoke a “spirit” that will tell us things that are hidden from our intellectual faculties.
Aleister Crowley, Book 4, Notes for an Astral Atlas