In the sixteenth and seventeenth century mysticism came to be used as a substantive.
Luther dismissed the allegorical interpretation of the bible, and condemned Mystical theology, which he saw as more Platonic than Christian.
The 19th century saw a growing emphasis on individual experience, as a defense against the growing rationalism of western society.
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.
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, religious traditions, and practices are joined together.