Esotericism refers to knowledge suitable only for the advanced, privileged, or initated, as opposed to exoteric knowledge, which is public. It is used especially of spiritual viewpoints.
Esotericism is from the Greek esoterikos, from esotero, the comparative form of eso, "within". It is a word meaning anything that is occult, a latinate word meaning "hidden" (from which we get the term occlusion). The opposite of this is exotericism, from the Greek exoterikos, from exotero, the comparative form of exo, "outside". Esotericism gives reference to anything private, specifically such things which are or were forced to be kept private due to fears of persecution.
Esotericism largely overlaps with occultism which simply means "hidden knowledge." However, in the 20th century many esotericists avoid the latter term owing to negative connotations associated with it (for example, the presumption that it involves devil-worship or black magic). For the same reason, many (predominantly Christian) opponents of esotericism prefer the term "occultism."
Much overlap exists as well between esotericism and mysticism. However, many mystical traditions do not attempt to introduce additional spiritual knowledge, but rather seek to focus the believer's attention or prayers more strongly upon the object of devotion. Thus Trappist monk Thomas Merton may be a mystic, but is probably not an esotericist.
The New Age movement has many links with various esoteric traditions. However, many esotericists disavow the "New Age" label, often because they reject many elements of the New Age movement (e.g., commercialism and/or naivite) and do not wish to be associated with it. Another difficulty is that of describing as "new" esoteric traditions that may be hundreds or even thousands of years old.
"Theosophy" means "divine wisdom" and once—in the writings of Jacob Boehme, for example—meant something similar to "esotericism." Today, however, it has come to refer to the Theosophical Society founded by H.P. Blavatsky, and other movements in this tradition.
Finally, culturally speaking, many followers of Satanism do probably belong under the general category of esotericism. However, these are shunned by practically everyone else, and for that matter their relationships with one another have been strained as well. Esotericism has far deeper ties--both historically and in the present day--with Christianity, though conservative Christian groups may be uncomfortable with the forms that this Christianity has taken.
Many religious movements in various parts of the world claim to possess a higher, truer, or better interpretation of the wider religion of which they are a part. Whether they are correct is inevitably a matter of controversy. Not infrequently, the claims of one esoteric group may be rejected by the wider religious culture, or by other esoteric groups which make their own rival claims.
While esotericism tends to focus on personal enlightenment and internal spiritual practice, organized religion or exotericism tends to focus on outer spiritual practice and ritual and on laws that govern the society. Nevertheless, esotericism also involves traditions, institutions, and other public aspects.
Esotericism is often said to assume the existence of a spiritual elite, as distinct from the believing masses. While many elements within esotericism are rooted in folk traditions--examples would include the Western study of magic and witchcraft--these have arguably become transformed into elite traditions by virtue of their appropriation by later antiquarians.
"Esotericism" often suggests an additional element of secrecy, for example the requirement that one be initiated before learning the higher truth (as in the case of the Freemasons). Note however that most "esoteric" teachings are widely available, and indeed often actively promoted. Some of this may be because it is now generally safer to promote alternative religious viewpoints than before.
Another possibility is that such knowledge may be kept secret not by the intention of its protectors, but by its very nature—for example, if it is accessible only to those with the proper intellectual or spiritual background. An example would be alchemy, success in which is said to involve copious amounts of study, practice, and spiritual preparation.
In some religious contexts, especially within Western Christianity, "esoteric" knowledge is seen as somewhat dangerous to the mainstream of that religion, involving the possibility of heresy. In other religious cultures such as Judaism, the leaders of the mainstream religion have historically also been recognized as the elite interpreters of its esoteric dimension, in this case Kabbalah.
The English word "esotericism" is usually applied to Western spiritual traditions. However, it has occasionally been used for non-Western religions, or more often, interpreted in such a way as to include such phenomena as yoga or tantra.
The criteria for inclusion under the label of "esoteric" are not always made explicit, and the result is often a matter of taste or historical usage. For example Emanuel Swedenborg, but not Mary Baker Eddy, is usually considered an esoteric figure, even though both developed their own inspired interpretations of the Bible.
Esotericism is not a single tradition but a vast array of often unrelated figures and movements. Nevertheless, the following may be helpful.
The Roman Empire gave birth not only to Christianity but also to a group of mystery religions which emphasized initiation. Some see Christianity, with its initiation ritual of baptism, as a mystery religion.
After Christianity became the state religion of Rome, dissident Christian groups became persecuted as traitors to the state. Also, pagan groups came to be suppressed as well. The terms "Gnosticism" and "Gnosis" have been challenged as coherent categories, but refer to a family of ancient Jewish, Christian, and pagan religious movements which often did claim to possess secret teachings relating to the spirit world, as opposed to the ordinary world which they tended to denegrate. Another important movement from the ancient world was Hermeticism, sometimes called Hermetism to distinguish it from post-Renaissance appropriations of it. Meanwhile, ancient Babylon provided the basis for Western astrology.
During the Middle Ages such things as astrology, alchemy, and magic were not distinct from the standard subjects of the curriculum of an educated man. While some people assume esotericism to be opposed to the Bible or Christianity, as a historical matter this tension would not arise until later. Indeed, Christianity contributed its own esoteric imagery, notably the Holy Grail from Arthurian literature .
While many esoteric subjects have a history reaching back thousands of years, these have generally not survived as continuous traditions. Rather, they have benefitted from various antiquarian revival movements. During the Italian Renaissance, for example, translators such as Ficino and Pico della Mirandola turned their attention to the classical literature of neo-Platonism, and what was thought to be the pre-Mosaic tradition of Hermeticism. Nineteenth-century writers turned their attention to earlier traditions of magic and witchcraft, often in conjunction with the various nationalisms of the day. An extreme example of this would be Nazi mysticism.
The influence of pietism, which emphasizes voluntary "extra" service to the divine above and beyond ordinary religious requirements, led to esoteric offshoots as well, such as Swedenborgianism.
Nineteenth-century esoteric writers came to be deeply influenced by various Eastern religions, which they typically saw as partaking of the same divine truth. Thus Madame Blavatsky could combine Indian philosophy with Western esoteric traditions of various types. In her view, the saints and mystics of all countries and ages (many of them otherwise unknown) cooperate in a common fraternity which resembles the lodges of Freemasonry as well as the original Rosicrucians, who were said to be "invisible." (Rosicrucianism was another tradition which enjoyed nineteenth-century revival.)
Important twentieth-century figures include Carl Gustav Jung, Fritjof Schuon , and Rene Guenon.
What, in a nutshell, does "esotericism" teach? No possible answer could do justice to the myriad groups which are subsumed under this name. However, we may venture some representative examples.
Many esoteric traditions do more or less the same things that mainstream religions do. Kabbalah for example preserves traditions describing the origin and destiny of humanity and the universe, as well as practices aimed at restoring ourselves and the world to our true stations.
Gnosticism teaches that this world is not our true home--that by seeing through the illusion and realizing our true nature, we can escape, returning to the world of spirit.
Hermeticism, including astrology, is based on the assumption that the soul and the cosmos are mysteriously and fundamentally linked. "As above, so below."
Freemasonry and some forms of alchemy use symbolic means to aid the practitioner in his individual betterment, with the aim of increasing virtue and drawing closer to the divine.
Theosophy and its offshoots teach the existence of hidden masters, who are charged with guiding earth's spiritual evolution. We may choose to actively cooperate with these efforts.
Spiritualism emphasizes the comfort of direct experience of the afterlife by means of communion with ghosts.
The Gurdjieff work teaches that people normally function like automatons, but can be taught to "wake up" via special practices which shake us out of our normal, mind-numbing habits.
Jungian psychology seeks to integrate the various dualities and contraries within a patient's psyche through involvement with myths, dreams, and visions.
As important a part of esotericism as any of these answers, is the spirit of quest which has encouraged seekers throughout the ages to search the world, and their own souls, for deeper meaning and ultimately salvation.
Many groups or schools of thought embrace an esoteric tradition or philosophy:
Esotericism in Popular Culture
The Harry Potter novels of J.K. Rowling contain numerous genuine esoteric references, notably that of the "philosopher's stone" from the first book.
Paolo Coelho 's novel "The Alchemist" involves a spiritual interpretation of alchemy.
Umberto Eco has written fiction with esoteric themes, notably the satirical novel Foucault's Pendulum.
The plot of Dan Brown's Da Vinci Code involves a centuries-old secret society called the Priory of Sion, charged with preserving certain secrets relating to Jesus Christ and the Merovingian kings.