THE AUSTRALIA & NEW ZEALAND SATANISTS ASSOCIATION
Wikipedia on Satanism....
In the Satanic Bible, Anton LaVey describes Satan as a motivating and balancing dark force in nature. Satan is also described as being the "Black Flame", representing a person's own inner personality and desires. Satan is seen as synonymous with the nature and even, metaphorically, with certain conceptions of a supreme deity or God.
In his most important essay, "Satanism: The Feared Religion", the Church of Satan's current leader Peter H. Gilmore states:
Satanists do not believe in the supernatural, in neither God nor the Devil. To the Satanist, he is his own God. Satan is a symbol of Man living as his prideful, carnal nature dictates. The reality behind Satan is simply the dark evolutionary force of entropy that permeates all of nature and provides the drive for survival and propagation inherent in all living things. Satan is not a conscious entity to be worshipped, rather a reservoir of power inside each human to be tapped at will. Thus any concept of sacrifice is rejected as a Christian aberration—in Satanism there’s no deity to which one can sacrifice.
Satan is said to appear in mythology and literature around the world as a trickster, rebel, and hero. Figures such as the Greek Prometheus are said to perfectly exemplify the qualities of Satan, the prideful rebel. Satan is seen as the powerful individual who acts regardless of what others might say. Also, the word satan is derived from the Hebrew for "adversary" or "accuser" (ha-satan). Thus, combining the traditional rebellious imagery associated with Satan and other relative deities, together with the etymological aspect of the word itself, Satanists claim to be adversaries of mainstream behavior which they define as "herd conformitY", seeing it as stifling to individuality, creativity, and progress.
Satanists do not believe that Satan is a god; rather, the function of God is performed and satisfied by the Satanist him/herself. That is, the needs of worship, ritual, and religious/spiritual focus are directed, effectively, inwards towards the Satanist, as opposed to outwards towards a God.
LaVey proposes, instead, that if all gods are creations of humans, worship of an external deity is worship of its creator by proxy. He suggests, then, that the rational Satanists should instead internalize their gods and therefore worship themselves; hence the Satanic maxim, "I am my own god."
It follows that Satanism shuns the idea of belief in all other deities as well. Belief in any such externalized deities is generally considered grounds for excluding someone as a Satanist, and devil worship in particular is considered nothing more than a misguided inversion of Christianity, and often dismissed as a Christian heresy.