Atheists do not belief in 'dieties' ... devine or holy beings with supernatural powers.
The term 'atheism' originated from the Greek word 'atheos', which means 'without gods'.
The first people who identified themselves as atheists go back as far as the 18th century.
There is no single ideology to which atheists apply themselves, and their arguments about religion range from philosophical to historical and social approaches. This arguments put them in a position where they don't have to proof anything, but put the burden of proof on the believer to proof that God exists.
However, Atheism are readily accepted into belief systems such as Hinduism and the spritual world of Wicca, as well as some forms of Buddhism.
It is difficult to determine how many atheists are in the world, because of the different perceptions that people have about Atheism. It was, however, estimated that about 2.3% of the world's population are atheists and 11.9% non-believers.
Satanism consists of diverse ideological and philosophical beliefs. It has a symbolic association and admiration for Satan, or similar rebellious and liberating figures.
The practice of Satanism began in 1966, when the Church of Satan was found. However, a group called Ophite Cultus Satanus predecents them, which was founded in 1948 by Herbert Athur Sloane in Ohio.
Contemporary Satanism is actually an American phenomenon, but quickly spread with the help of globalization and the Internet. Satanism started to reach Eastern Europe in the early 1990's, in the time when the Soviet Union fell, and is most noticable in Poland and Lithuania, which was actually dominated by the Roman Catholic Church.
a. Theistic Satanism
It is also known as traditional Satanism or Devil Worship.
It consists of
1. Luciferianism ... a belief system in the inherent characteristics commonly given to Lucifer, which is commonly identified with Satan.
2. Palladists ... an alleged theistic [believe in supernatural beings] Satanist society.
3. Our Lady of Endor Coven ... also known as Ophite Cultus Satanus, which was heavily influenced by the gnosticism belief that the spiritual world should be embraced. They worshipped Satanus [their name for Satan], and 'Ophite' refers to an ancient gnostic sect, and it was said that they worshipped the serpent.
b. Atheistic Satanism
1. La Veyan Satanism ... atheists who regard Satan as a symbol of man's inherent nature.
2. Symbolic Satanism ... views Satan as a symbolic or mythic archetype [form]. They admire the archetype [form] as the 'Adversary' or 'Light Bringer'.
c. Casual Satanism
They use symbols like the inverted pentagram, black mass and demonic images to provide a impression of Satanism.
This is a threshold experience for its shock value and does not neccessarily indicate belief or interest in the various forms of Satanist practice cited above.
It is not quite clear how many members there are in the world, but was estimated at 50 000 members in 1990.