A belief system is a set of mutually supportive belief

Belief

Belief is the psychological state in which an individual holds a proposition or premise to be true.-Belief, knowledge and epistemology:The terms belief and knowledge are used differently in philosophy....

s. The beliefs may be religious

Religious belief

Religious belief is a strong belief in a supernatural power or powers that control human destiny. Such a state may relate to the existence, characteristics and worship of a deity or deities, divine intervention in the universe and human life, or values and practices centered on the teachings of a...

, philosophical

Philosophy

Philosophy is the study of general and fundamental problems, such as those connected with existence, knowledge, values, reason, mind, and language. Philosophy is distinguished from other ways of addressing such problems by its critical, generally systematic approach and its reliance on rational...

, ideological

Ideology

An ideology is a set of ideas that constitutes one's goals, expectations, and actions. An ideology can be thought of as a comprehensive vision, as a way of looking at things , as in common sense and several philosophical tendencies , or a set of ideas proposed by the dominant class of a society to...

 or a combination of these.

The British philosopher Stephen Law

Stephen Law

Dr. Stephen Law is a philosopher and senior lecturer at Heythrop College in the University of London. He also edits the philosophical journal Think, which is published by the Royal Institute of Philosophy and aimed at the general public. Law currently lives in Oxford, England, with his wife and two...

 has described some belief systems (including belief in homeopathy

Homeopathy

Homeopathy is a form of alternative medicine in which practitioners claim to treat patients using highly diluted preparations that are believed to cause healthy people to exhibit symptoms that are similar to those exhibited by the patient...

, psychic powers and alien abduction) as "claptrap" and said that they "draw people in and hold them captive so they become willing slaves ... if you get sucked in, it can be extremely difficult to think your way clear again".