<P> Yet such spiritually - informed treatment approaches have been challenged as pseudoscience, are far from uniformly curative and may for non-believers cause harm (see iatrogenesis). </P> <P> "Spiritual experience" plays a central role in modern spirituality . This notion has been popularised by both western and Asian authors . Important early 20th century western writers who studied the phenomenon of spirituality, and their works, include William James, The Varieties of Religious Experience (1902), and Rudolph Otto, especially The Idea of the Holy (1917). James' notions of "spiritual experience" had a further influence on the modernist streams in Asian traditions, making them even further recognisable for a western audience . </P> <P> William James popularized the use of the term "religious experience" in his The Varieties of Religious Experience . It has also influenced the understanding of mysticism as a distinctive experience which supplies knowledge . </P> <P> Wayne Proudfoot traces the roots of the notion of "religious experience" further back to the German theologian Friedrich Schleiermacher (1768--1834), who argued that religion is based on a feeling of the infinite . The notion of "religious experience" was used by Schleiermacher to defend religion against the growing scientific and secular critique . It was adopted by many scholars of religion, of which William James was the most influential . </P>

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