“Baptista Porta, in his treatise on Natural Magic, enumerates a whole catalogue of secret formulae for producing extraordinary effects by employing the occult powers of nature.
Although the “magicians” believed as firmly as our spiritualists in a world of invisible spirits, none of them claimed to produce his effects under their control or through their sole help. They knew too well how difficult it is to keep away the elementary creatures when they have once found the door wide open.
Even the magic of the ancient Chaldeans was but a profound knowledge of the powers of simples and minerals. It was only when the theurgist desired divine help in spiritual and earthly matters that he sought direct communication through religious rites, with pure spiritual beings.
With them, even, those spirits who remain invisible and communicate with mortals through their awakened inner senses, as in clairvoyance, clairaudience and trance, could only be evoked subjectively and as a result of purity of life and prayer.
But all physical phenomena were produced simply by applying a knowledge of natural forces, although certainly not by the method of legerdemain practiced in our days by conjurers.”
H. P. Blavatsky