The word has many uses in the English language, popularly meaning "knowledge of the paranormal", as opposed to "knowledge of the measurable", usually referred to as science. The term is sometimes popularly taken to mean "knowledge meant only for certain people" or "knowledge that must be kept hidden", but for most practicing occultists it is simply the study of a deeper spiritual reality that extends beyond pure reason and the physical sciences. The terms esoteric and arcane can have a very similar meaning, and the three terms are often interchangeable.
The term occult is also used as a label given to a number of magical organizations or orders, and the teachings and practices as taught by them. The name also extends to a large body of literature and spiritual philosophy.
The word "occult" is somewhat generic, in that almost everything that isn't claimed by any of the major religions can be considered the occult. Even religious scientists have difficulties in defining occultism. A broad definition is offered by Nicholas Goodrick-Clarke:
"OCCULTISM has its basis in a religious way of thinking, the roots of which stretch back into antiquity and which may be described as the Western esoteric tradition. Its principal ingredients have been identified as Gnosticism, the Hermetic treatises on alchemy and magic, Neo-Platonism, and the Kabbalah, all originating in the eastern Mediterranean area during the first few centuries AD.
From the 15th to 17th century, these kinds of ideas had a brief revival, that was halted by the triumph of empirical sciences in the seventeenth-century. "By the eighteenth century these unorthodox religious and philosophical concerns were well defined as 'occult', inasmuch as they lay on the outermost fringe of accepted forms of knowledge and discourse," and were only preserved by a few antiquarians and mystics. However, from about 1770 onwards, a renewed desire for mystery, an interest in the Middle Ages and a romantic temper encouraged a revival of occultism in Europe, "a reaction to the rationalist Enlightenment." In this concept, occultism largely overlaps with the scope of Western esotericism, as already indicated in the quote.
Based on his research into the the modern German occult revival 1890-1910, Goodrick-Clarke puts forward a thesis on the driving force behind occultism. Behind its many varied forms apparently lies a uniform function, "a strong desire to reconcile the findings of modern natural science with a religious view that could restore man to a position of centrality and dignity in the universe.
That the Kabbalah has been considered an occult study is also perhaps because of its popularity among magi (the biblical wise men who visited the Infant Jesus are said to have been magi of Zoroastrianism) and Thelemites. Kabbalah was later adopted by the Golden Dawn and brought out into the open by Aleister Crowley and his protégé Israel Regardie. Since that time many authors have emphasized a syncretic approach by drawing parallels between different disciplines.
Direct insight into or perception of the occult does not consist of access to physically measurable facts, but is arrived at through the mind or the spirit. The term can refer to mental, psychological or spiritual training. It is important to note, however, that many occultists will also study science (perceiving science as a branch of Alchemy) to add validity to occult knowledge in a day and age where the mystical can easily be undermined as flights-of-fancy. An oft-cited means of gaining insight into the occult is the use of a focus. A focus may be a physical object, a ritualistic action (for example, meditation or chanting), or a medium in which one becomes wholly immersed; these are just a few examples of the vast and numerous avenues that can be explored.
In Judaism, special spiritual studies such as Kabbalah have been allowed for certain individuals (such as rabbis and their chosen students). These studies do not conform to mainstream Jewish ritual. Also, some forms of Islam allow spirits to be commanded in the name of Allah to do righteous works and assist steadfast Muslims. Furthermore, there are branches of Esoteric Christianity that practice divination, blessings, or appealing to angels for certain intervention, which they view as perfectly righteous, often supportable by gospel (for instance, claiming that the old commandment against divination was superseded by Christ's birth, and noting that the Magi used astrology to locate Bethlehem). Rosicrucianism, one of the most celebrated of Christianity's mystical offshoots, has lent aspects of its philosophy to most Christian-based occultism since the 17th century.
Tantra, originating in India, includes amongst its various branches a variety of ritualistic practices ranging from visualisation exercises and the chanting of mantras to elaborate rituals involving sex or animal sacrifice, sometimes performed in forbidden places such as cremation grounds. Tantric texts were at one stage unavailable for mass public consumption due to the social stigma attached to the practices. In general, tantra was predominantly associated with black magic and the tantriks were held in great dishonor.