Hellenistic world
In the Hellenistic world, 'mystical' referred to "secret" religious rituals like the Eleusinian Mysteries.[web 2] The use of the word lacked any direct references to the transcendental.[12] A "mystikos" was an initiate of a mystery religion.

Early Christianity
Main articles: Greco-Roman mysteries, Early Christianity, and Esoteric Christianity
In early Christianity the term "mystikos" referred to three dimensions, which soon became intertwined, namely the biblical, the liturgical and the spiritual or contemplative.[1] The biblical dimension refers to "hidden" or allegorical interpretations of Scriptures.[web 2][1] The liturgical dimension refers to the liturgical mystery of the Eucharist, the presence of Christ at the Eucharist.[web 2][1] The third dimension is the contemplative or experiential knowledge of God.[1]

Until the sixth century, the Greek term theoria, meaning "contemplation" in Latin, was used for the mystical interpretation of the Bible.[9] The link between mysticism and the vision of the Divine was introduced by the early Church Fathers, who used the term as an adjective, as in mystical theology and mystical contemplation.[12] Under the influence of Pseudo-Dionysius the Areopagite the mystical theology came to denote the investigation of the allegorical truth of the Bible,[1] and "the spiritual awareness of the ineffable Absolute beyond the theology of divine names."[36] Pseudo-Dionysius' Apophatic theology, or "negative theology", exerted a great influence on medieval monastic religiosity.[37] It was influenced by Neo-Platonism, and very influential in Eastern Orthodox Christian theology. In western Christianity it was a counter-current to the prevailing Cataphatic theology or "positive theology".

Theoria enabled the Fathers to perceive depths of meaning in the biblical writings that escape a purely scientific or empirical approach to interpretation.[38] The Antiochene Fathers, in particular, saw in every passage of Scripture a double meaning, both literal and spiritual.[39]

Later, theoria or contemplation came to be distinguished from intellectual life, leading to the identification of θεωρία or contemplatio with a form of prayer[40] distinguished from discursive meditation in both East[41] and West.[42]

Medieval meaning
See also: Middle Ages
This threefold meaning of "mystical" continued in the Middle Ages.[1] According to Dan Merkur, the term unio mystica came into use in the 13th century as a synonym for the "spiritual marriage," the ecstasy, or rapture, that was experienced when prayer was used "to contemplate both God’s omnipresence in the world and God in his essence."[web 1] Under the influence of Pseudo-Dionysius the Areopagite the mystical theology came to denote the investigation of the allegorical truth of the Bible,[1] and "the spiritual awareness of the ineffable Absolute beyond the theology of divine names."[36] Pseudo-Dionysius' Apophatic theology, or "negative theology", exerted a great influence on medieval monastic religiosity, although it was mostly a male religiosity, since women were not allowed to study.[37] It was influenced by Neo-Platonism, and very influential in Eastern Orthodox Christian theology. In western Christianity it was a counter-current to the prevailing Cataphatic theology or "positive theology". It is best known nowadays in the western world from Meister Eckhart and John of the Cross.

Early modern meaning
See also: Early modern period

The Appearance of the Holy Spirit before Saint Teresa of Ávila, Peter Paul Rubens
In the sixteenth and seventeenth century mysticism came to be used as a substantive.[12] This shift was linked to a new discourse,[12] in which science and religion were separated.[43]

Luther dismissed the allegorical interpretation of the bible, and condemned Mystical theology, which he saw as more Platonic than Christian.[44] "The mystical", as the search for the hidden meaning of texts, became secularised, and also associated with literature, as opposed to science and prose.[45]

Science was also distinguished from religion. By the middle of the 17th century, "the mystical" is increasingly applied exclusively to the religious realm, separating religion and "natural philosophy" as two distinct approaches to the discovery of the hidden meaning of the universe.[46] The traditional hagiographies and writings of the saints became designated as "mystical", shifting from the virtues and miracles to extraordinary experiences and states of mind, thereby creating a newly coined "mystical tradition".[2] A new understanding developed of the Divine as residing within human, an essence beyond the varieties of religious expressions.[12]

Contemporary meaning
See also: Western esotericism, Theosophy (Blavatskian), Syncretism, Spirituality, and New Age
The 19th century saw a growing emphasis on individual experience, as a defense against the growing rationalism of western society.[19][web 1] The meaning of mysticism was considerably narrowed:[web 1]

The competition between the perspectives of theology and science resulted in a compromise in which most varieties of what had traditionally been called mysticism were dismissed as merely psychological phenomena and only one variety, which aimed at union with the Absolute, the Infinite, or God—and thereby the perception of its essential unity or oneness—was claimed to be genuinely mystical. The historical evidence, however, does not support such a narrow conception of mysticism.[web 1]

Under the influence of Perennialism, which was popularised in both the west and the east by Unitarianism, Transcendentalists and Theosophy, mysticism has been applied to a broad spectrum of religious traditions, in which all sorts of esotericism and religious traditions and practices are joined together.[47][48][19] The term mysticism was extended to comparable phenomena in non-Christian religions,[web 1] where it influenced Hindu and Buddhist responses to colonialism, resulting in Neo-Vedanta and Buddhist modernism.[48][49]

In the contemporary usage "mysticism" has become an umbrella term for all sorts of non-rational world views,[50] parapsychology and pseudoscience.[51][52][53][54] William Harmless even states that mysticism has become "a catch-all for religious weirdness".[55] Within the academic study of religion the apparent "unambiguous commonality" has become "opaque and controversial".[12] The term "mysticism" is being used in different ways in different traditions.[12] Some call to attention the conflation of mysticism and linked terms, such as spirituality and esotericism, and point at the differences between various traditions.[56]