In the Ophite sect of early Christianity, the Serpent was praised as the giver of knowledge. Sometimes Satan was also referred to, under the names Lucifer or "the light-bringer", but others see this as incorrect because they believe that Satan and Lucifer are two sperate entites. Some Gnostics claimed that the being declared God by Christians and Jews was in fact lesser being known as the Demiurge, whose name derives from the creator figure in Plato's Timaeus; a very few Gnostic sects identified this figure with Satan; others (such as the Valentinians) saw Satan as a subsequent creation of the Demiurge.

Some early Gnostic sects, such as the Borborites and the followers of Carpocrates, were accused of horrific acts, including the eating (in horrific imitation of the sacrament) of semen, menses and aborted fetuses. These acts were committed with the apparent justification of libertinism; given that the material universe was not God's creation, it could be put to any use with no moral consequences. Accounts of these barbaric acts are not held to be at all credible, as the accusations were rhetorical attacks against these groups by such heresiological writers as Irenaeus.

However, Gnostic sects were commonly more liberal in nature than emergent orthodox groups; for example, in viewing sexual congress as a good, even a potentially spiritual act, and in allowing woman priests and bishops to administer sacraments. There is evidence that Valentinians performed a religious ceremony known as the Bridal Chamber, in which the physical union of a man and woman was viewed as an earthly reenactment of God's completeness; the Gnostic conception of the divine was as an androgyne, as opposed to the orthodoxy identification of him as male. Such criticisms as Irenaeus' may be the deliberate exagerration of these misdeeds (from the point of view of orthodoxy). The Order of Nine Angles (ONA) has labeled itself Traditional Satanist and considers Satanism to be an individual quest which goes far beyond the gratification of the pleasure-principle and involves the arduous achievement in a Nietzschean sense, with the aim of cosmic wisdom. Their conception of Satanism is practical, with an emphasis on individual growth into realms of darkness and danger through risky acts of prowess. In addition, the ONA seek to change, and disrupt, society itself. They espouse human sacrifice, which they see as the culling of "offers," victims who are chosen according to strict guidelines. The use of the term "traditional" by these Satanists (ONA) is viewed by some as improper because the ONA refuses to provide any evidence of an old tradition, countering that it is the duty of each initiate to work things out for themselves. In addition, it is felt that "Traditional Satanism" as a label applies better, or at least equally well, to parts of the gnostic movement and its modern remnants.

The Misanthropic Luciferian Order is a Scandinavian example of a Neo-Gnostic Satanic current. The MLO is a Chaos-Gnostic Order that "seeks the true Light of Lucifer through the study, development and practice of all forms of dark, gnostic and Satanic Magical systems".

The Norwegian Satanic Society, also known as DNSS, was the first LaVey-Satanic society in Norway and represents a more liberal or social-democratic Satanism, as writer Didrik Soderlind said it, compared to the more classic American Satanism.

Ordo Illuminatorum is a Norwegian concept of Satanic illumination, which is set up by The Norwegian Satanic Society and Norwegian Satanic Temple, also known as NST. NST represents the philosophy of DNSS as well, but is more involved in the process of interaction between Satanists. Ordo Templi Satanas is the social network of lodges throughout the country, thus making it possible to interact socially with other Satanists.

In early 2004, John L. Westbrook, a former Oklahoma politician told a Penthouse reporter that he had formed an "occult fraternity, to finish the work that the Temple of Set has previously botched." He then displayed a platinum medallion which he had commissioned that resembled a Mars planetary sigil. He has christened this neo-Satanic fraternity The Order of Mars. He said membership in his "fraternity" is restricted to those whom he knows personally and that his group does not solicit memberships. He also stated that this "Order" is named in honor of the Roman god Mars, whom he claims is closely aligned with Egyptian god Set.

The Sinagogue of Satan is an organization of the religion founded by Reverend Michael S. Margolin based on the Ancient and Accepted Rite of Free Masonry's definition of Satanism as described in Albert Pike's work Morals and Dogma. This religion is not based on those of the popular Satanists of our day, nor Hollywood and Christian propaganda, except for Aleister Crowley. The religion contains no dogma in or of itself, and encourages its followers to believe in whatever they like, as long as they do not attempt to push such beliefs on others. The aim of this religion is the ultimate destruction of religions through the advancement of individual freedom and social responsibility. The Sinagogue of Satan does not promote self-indulgence (in contrast to LaVeyan Satanism), but rather self-expression balanced with social responsibility.

Another organization practicing in Modern, or LaVeyan Satanism is the True Church of Satan, (aka TCOS) which is an organization "based on the original principles of Satanism as it was founded in April of 1966." The TCOS is not associated or affiliated with the current Church of Satan or any other organization, although the group is rumoured to have ties to the secretive Chicago-based "Black Blood Grotto", another Fundamental Satanist group. They believe that "The Satanic Bible is the inspired Word of Anton Szandor LaVey and is the basis for any statement of belief in Satanism as a religion. The church subscribes to the doctrinal statement of The Satanic Bible and Message as adopted by the original Magic Circle in 1966...This church is comprised of persons who profess a understanding of Satanic Law." They refer to their form of practice as "True Satanism", also called "Fundamental Satanism", i.e. basing their form of religion only on texts written in or derived from the orginal "Baphomet Trilogy" (The Satanic Bible, The Satanic Witch,The Satanic Rituals, with The Devil's Notebook being an addendum) set of books by Anton Szandor LaVey. They consider other texts, even those written personally by A.S. LaVey to be examples of Satanic Freedom, but not part of the Tenets of Satanism, or Lex Satanicus (Satanic law).

LaVey's "9 Satanic Statements", a philosophical outline to defining Satanism in The Satanic Bible, were as follows:
1.Satan represents indulgence instead of abstinence.
2.Satan represents vital existence instead of spiritual pipe dreams.
3.Satan represents undefiled wisdom instead of hypocritical self-deceit.
4.Satan represents kindness to those who deserve it instead of love wasted on ingrates.
5.Satan represents vengeance instead of turning the other cheek.
6.Satan represents responsibility to the responsible instead of concern for psychic vampires.
7.Satan represents man as just another animal, sometimes better, more often worse than those that walk on all-fours, who, because of his “divine spiritual and intellectual development,” has become the most vicious animal of all.
8.Satan represents all of the so-called sins, as they all lead to physical, mental, or emotional gratification.
9.Satan has been the best friend the Church has ever had, as he has kept it in business all these years.

Matching these, LaVey also identified 9 Satanic sins, namely:
Stupidity, pretentiousness (putting on airs), solipsism (expecting others to give back to you what you give to them), self-deceit, herd conformity, lack of perspective, forgetfulness of past orthodoxies (i.e. accepting something as new and different which is merely a repackaging of the old or the discredited), counterproductive pride (i.e. pride of a type which undermines one's own goals), and lack of aesthetics.

Note: solipsism can also refer to an epistemological idea attributed to Descartes, suggesting that one person is the only one to actually experience existence and that all others are merely figments of the imagination of this individual.

He further outlined 11 Satanic rules, which while not exactly a moral code, provide Satanists with general guidelines for living:
1.Do not give opinions or advice unless you are asked.
2.Do not tell your troubles to others unless you are sure they want to hear them.
3.When in another’s lair, show him respect or else do not go there.
4.If a guest in your lair annoys you, treat him cruelly and without mercy.
5.Do not make sexual advances unless you are given the mating signal.
6.Do not take that which does not belong to you unless it is a burden to the other person and he cries out to be relieved.
7.Acknowledge the power of magic if you have employed it successfully to obtain your desires. If you deny the power of magic after having called upon it with success, you will lose all you have obtained.
8.Do not complain about anything to which you need not subject yourself.
9.Do not harm little children.
10.Do not kill non-human animals unless you are attacked or for your food.
11.When walking in open territory, bother no one. If someone bothers you, ask him to stop. If he does not stop, destroy him.

It is interesting to note that some of these rules appear opposite to traits commonly perceived as "Satanic." Specifically, proselytism (in this case, actively turning others to the worship of Satan) is strongly discouraged, and the prohibition of harm against children and animals contradicts reputed Satanic fondness for sacrifice (see Satanic Ritual Abuse), both of which are often erroneously associated with Satanists.

Much criticism arises from the major religions, although most has come from Christianity. There has been both constructive debate and open hostility, with the latter sometimes stemming from the Christian countercult movement in books by Lauren Stratford, Mike Warnke, and Bob Larson.
The claim that Satanism is purely reactionary as a religion and philosophy, and as such can only be defined by its opposition to what is perceived as the hypocritical, stupid, tired, weak, and boring failings of mainstream philosophies and religions. It also draws its whole understanding of the meaning and nature of Satan or Satanic worship from the literature which it intends to oppose. Rev. D.R. Deinsen notes that Satanist writers of the internet sound like "enraged, frustrated teenagers who need a target to pin their angst on and need one now." .
Many Satanists identify with Satan as a rebellious force. However, it is claimed that such identification relies on the acceptance of a supreme being, authority, or creator to rebel against. It is claimed that if one has accepted the presence of such a being, that only falsehood on the part of the will can lead to rebellion against it.
Christian theologians argue that it is impossible for a human being to indulge completely in Satanic evil, for they believe that all human evil is a corrupted attempt to do something good (eg. to further the gratification or security of one's ownself, even if this is at the expense of others). Even a hedonist attempts to seek that recognised as good, if only for himself. These theologians claim that only pain, confusion, isolation and disappointment can result when such attempts are not in accord with the laws of God (i.e. vices or sins).
Satanism is "philosophy light" and "rhetoric heavy." Anton LaVey’s greatest skill is said to have been that of a rhetorician. Satanism, so it is argued, proves to be an intellectually shallow glamourisation of human divinity.
The argument that "people need people". Some claim that Satanists misunderstand independence and that while individually, independence may make you stronger, it is impossible to be independently a god. They claim that declaring oneself a god, while beneficial for self-esteem, can lead to a denial of the reality.
An alternate form of the criticism points out that while Satanism usually presents itself as a necessary cure for a passive herd mentality promoted by mainstream religions, its emphasis on the merits of independence and individualism can itself lead to abuse of a different kind - and, according to some critics, it usually does. Due to its own individualistic nature, Satanism tends to be deficient in the social feedback and regulation that traditional religions often employ to correct their own excesses.

There are many groups which are commonly misconceived as Satanic. There are two common definitions of a Satanic religion:
Any religion that consciously recognizes and worships "Satan," usually referring either to a "dark" deity (similar to the Christian Satan, though usually lacking the evil or unnaturalness associated with it) or a conceptual Satan, often referring to a so-called "true" nature of Mankind.
Some religions that do not follow the Christian religion or recognize Jesus as explained in the Christian creeds.

The second definition is most commonly used by fundamentalist Christians, and is the source of much disagreement about whether a religion should be considered Satanic or not. The most common targets of these claims are Neo-Pagan religions, such as Wicca and Ásatrú.

Occasionally, some Christian denominations or even Judaism and Islam are referred to as Satanic, based on interpretations of the second definition. Among these Christian groups are usually the less traditional ones, such as the Mormons and other smaller sects. Also, it is not unheard of for Catholics to refer to Protestants as Satanic, and vice versa, though this is more uncommon.

Another movement which is wrongly associated with Satan is heavy rock and metal music. Although there are some music groups that intentionally use Satanic imagery for one reason or another, the vast majority of metal/rock bands have no connection to any sort of Satanic philosophy.

The Process Church is an example of a group that has been labelled Satanic but rejected that label. The Process Church worshipped Satan, but they believed that he had repented of his misdeeds and had become reconciled to God and to his brother Jesus Christ. Their concept of Satan-worship is so different from that of other Satanists that the label does not apply to them.

Another group is the Kurdish religion Yazidi. They worship the angel Melek Taus, sometimes also called the "peacock angel". Christians and Muslim identify this angel with Satan; the Yazidis themselves are very unclear about his status, sometimes identifying him with the Christian/Muslim Satan, othertimes denying that he has anything to do with their Satan, but commonly naming him as the very first being created by god.