Satan in Paradise Lost, as illustrated by Gustave Doré
Particularly after the European Enlightenment, some works, such as Paradise Lost, were taken up by Romantics and described as presenting the biblical Satan as an allegory representing a crisis of faith, individualism, free will, wisdom and enlightenment. Those works actually featuring Satan as a heroic character are fewer in number, but do exist; George Bernard Shaw, and Mark Twain (cf. Letters from the Earth) included such characterizations in their works long before religious Satanists took up the pen. From then on, Satan and Satanism started to gain a new meaning outside of Christianity.
Although the public practice of Satanism began in 1966 with the founding of the atheistic Church of Satan, some historical precedents exist: a group called the Ophite Cultus Satanas was founded in Ohio by Herbert Arthur Sloane in 1948. Inspired by Gnosticism and Gerald Gardner's Wicca, the coven venerated Satan as both a horned god and ophite messiah.
Satanist groups that appeared after the 1960s are widely diverse, but two major trends are Theistic Satanism and atheistic Satanism. Theistic Satanists venerate Satan as a supernatural deity. In contrast, Atheistic Satanists consider themselves atheists, agnostics, ignostics or apatheists and regard Satan as merely symbolic of certain human traits. This categorization of Satanism (which could be categorized in other ways, for example "Traditional" versus "Modern"), is not necessarily adopted by Satanists themselves, who usually do not specify which type of Satanism they adhere to. Some Satanists believe in a god in the...