The Doors of Perception is an autobiographical book written by Aldous Huxley. Published in 1954, it elaborates on his psychedelic experience under the influence of mescaline in May 1953. Huxley recalls the insights he experienced, ranging from the "purely aesthetic" to "sacramental vision", and reflects on their philosophical and psychological implications. In 1956, he published Heaven and Hell, another essay which elaborates these reflections further. The two works have since often been published together as one book; the title of both comes from William Blake's 1793 book The Marriage of Heaven and Hell. The Doors of Perception provoked strong reactions for its evaluation of psychedelic drugs as facilitators of mystical insight with great potential benefits for science, art, and religion. While many found the argument compelling, others including German writer Thomas Mann, Vedantic monk Swami Prabhavananda, Jewish philosopher Martin Buber, and Orientalist scholar Robert Charles Zaehner countered that the effects of mescaline are subjective and should not be conflated with objective religious mysticism. Huxley himself continued to take psychedelics for the rest of his life, and the understanding he gained from them influenced his final novel Island, published in 1962. Background Mescaline (peyote and San Pedro cactus) Mescaline is the principal active psychedelic agent of the peyote and San Pedro cacti, which have been used in Native American religious ceremonies for thousands of years. A German pharmacologist, Arthur Heffter, isolated the alkaloids in the peyote cactus in 1897. These included mescaline, which he showed through a combination of animal and self-experiments was the compound responsible for the psychoactive properties of the plant. In 1919, Ernst Späth, another German chemist, synthesised the drug. Although personal accounts of taking the cactus had been written by psychologists such as Weir Mitchell in the US and Havelock Ellis in the UK during the 1890s, the German-American Heinrich Klüver was the first to systematically study its psychological effects in a small book called Mescal and Mechanisms of Hallucinations published in 1928. The book stated that the drug could be used to research the unconscious mind. In the 1930s, an American anthropologist Weston La Barre, published The Peyote Cult, the first study of the ritual use of peyote as an entheogen drug amongst the Huichol people of western Mexico. La Barre noted that the Native American users of the cactus took it to obtain visions for prophecy, healing and inner strength. Most psychiatric research projects into