The most hostile to metaphysics of the works by Immanuel Kant, an 18th-century German philosopher, one of the foremost thinkers of the Enlightenment. Published in 1766 anonymously, Dreams of a Spirit Seer (Träume eines Geistersehers), the book deals with the speculations of Crusius and Wolff as spun out of nothing, like the spiritual imaginings of Swedenborg – famous Swedish scientist and inventor, who announced himself to be a visionary. He assured to be able to communicate with souls of dead people and get information from another world. Swedenborg was the subject of numerous unbelievable stories, some of which Kant ironically presents in the book, seeing in such tales just quaint fancy. However this work was not only intended against Swedenborg, but was also touches upon other metaphysicians, who take their visions for reality, and combinations of thoughts for present order. Kant pronounces a sentence to any system of speculative conclusion, calling people of science to trust only the experience. In the conclusive part of the work the author deals with problems of causality.