S. L. MacGregor Mathers 
Sacred Magic Of Abramelin The Mage [EPUB ebook] 

The particular scheme or system of Magic advocated in the present work is to an extent ‘sui generis’ but to an extent only. It is rather the manner of its application which makes it unique. In Magic, that is to say, the Science of the Control of the Secret Forces of Nature, there have always been two great schools, the one great in Good, the other in Evil the former the Magic of Light, the latter that of Darkness the former usually depending on the knowledge and invocation of the Angelic natures, the latter on the method of evocation of the Demonic races. Usually the former is termed White Magic, as opposed to the latter, or Black Magic.
The invocation of Angelic Forces, then, is an idea common in works of Magic, as also are the Ceremonies of Pact with and submission to the Evil Spirits. The system, however, taught in the present work is based on the following conception:
That the Good Spirits and Angelic Powers of Light are superior in Power to the Fallen Spirits of Darkness.
That these latter as a punishment have been condemned to the service of the Initiates of the Magic of Light. (This Idea is to be found also in the Kôran; or, as it is frequently and perhaps more correctly written, ‘Qûr-an’.)
As a consequence of this doctrine, all ordinary material effects and phenomena are produced by the labour of the Evil Spirits under the command usually of the Good.
That consequently whenever the Evil Demons can escape from the control of the Good, there is no evil that they will not work by way of vengeance.
That therefore sooner than obey man, they will try to make him their servant, by inducing him to conclude Pacts and Agreements with them.
That to further this project, they will use every means that offers to obsess him.
That in order to become an Adept, therefore, and dominate them; the greatest possible firmness of will, purity of soul and intent, and power of self-control is necessary.
That this is only to be attained by self-abnegation on every plane. That man, therefore, is the middle nature, and natural controller of the middle nature between the Angels and the Demons, and that therefore to each man is attached naturally both a Guardian Angel and a Malevolent Demon, and also certain Spirits that may become Familiars, so that with him it rests to give the victory unto the which he will.
That, therefore, in order to control and make service of the Lower and Evil, the knowledge of the Higher and Good is requisite.