"The science that deals with things that transcend sensual perception (non-observable) and are generally little known. It deals especially with effects that cannot be explained by the universally known laws of Nature, but whose causes are still a mystery to those who have not penetrated deep enough into the secrets of Nature to understand them correctly. What may be occult to one person, may be fully comprehensible to another. The more the spirituality and intelligence of man grows and the more it becomes free of the attractions of sense, the more will his perceptive power grow and expand, and the less will the processes of Nature appear occult to him. What is occult is a mystery hence mysticism or the search to understand mystery or that which is occulted to view or understanding." [Hartmann, Franz; The Life of Philippus Theophrastus, Bombast of Hohenheim, Known by the name of Paracelsus and The Substance of His Teachings, George Redway, London, 1887]
"Occultism is the ancient science which deals with the hidden forces of nature, the laws governing them, and the means by which such forces can be brought under the control of the enlightened human mind.
An occultist is one who believes in the reality of esoteric sciences, has studied them in a scholarly manner, has resolved to perfect his own consciousness according to their rules, and may, or may not, be able to practice the rituals and formulas of Transcendental Magic." [Manly Palmer Hall]