The concept of Satan has evolved over the centuries, as has Satanism.

Originally in Judeo-Christian traditions, Satan was seen as a part of creation, embodying the principle that one could choose contrary to God's wishes, and thus empowering the potential for freewill and defiance. (In this context an ancient Jewish commentary notes that only when the potential to contravene God's will arose, could creation become "very good" as opposed to merely "good"). Over the centuries this concept of Satan came to embody all that was evil and against God, a change attributable to two main influences:

• The view that everything had its opposite, and that God, all-good, must have His opposing deity too (many preceding multiple deity religions also had their evil gods as well as good gods, Set of the Ancient Egyptians being one example),
• The spreading of Christianity, followed by Islam, both religions which gained a wide number of adherents, which placed a high premium on salvation and the afterlife, and within which Satan grew as an embodiment of all that was trying to undermine God in this theological world-view.

As society evolved from the reformation into the enlightenment onwards (17th and 18th centuries), people in Western societies began to question the nature of evil, and Satan gradually evolved yet again in response to this, so Satanism came to signify a tradition which denied traditional religious paths in favor of a self-oriented path, rather than a path which favored evil.

In an older sense, Satanism also refers to unorthodox practices within Abrahamic religions deemed by an orthodoxy to be in opposition to the Abrahamic God. The earliest recorded instance of the word is in "A confutation of a booke (by Bp. Jewel) entitled An apologie of the Church of England", by Thomas Harding (1565): ll, ii, 42 b, "Meaning the time when Luther first bringed to Germanie the poisoned cuppe of his heresies, blasphemies, and Satanismes." As Martin Luther himself would have denied any link between his teachings and Satan, this use of the term Satanism was primarily pejorative. Many Satanists find such use of the term offensive.