The article focuses on the two aspects of alchemical philosophy — spiritual and practical. It overviews the works of all main periods in the history of the Western alchemy, from early Greek authors to the 20th century alchemists. The author deals with spiritual speculations and laboratory practices of most important alchemical philosophers. This includes such names as Zosimos of Panopolis, Robert of Chester, Roger Bacon, Pseudo-Geber, Joannes Rupescissa, Ole Borch, Edward Kelly, and Robert Boyle; then follow some modern alchemists such as Cyliani, Fulcanelli, Frater Albertus, Mark Stavish, and others. Spiritual and practical alchemy of the medieval and later periods is analyzed in terms of its influence on modern science. The article then provides a general approach to the transformation of «modern alchemy» in the 19th-20th centuries.