Alchemy (from Arabic: al-kīmiyā) is an ancient branch of natural philosophy, a philosophical and protoscientific tradition practiced throughout Europe, Africa, China and throughout Asia, originating in Chinese text, around 73-49 BC and Greco-Roman Egypt in the first few centuries CE.
The common perception of alchemists is that they attempted to turn lead into gold, believed all matter was composed of the four elements of earth, air, fire, and water, and dabbled around the edges of mysticism and magic. They were attempting to explore and investigate nature before many of the most basic scientific tools and practices were available, relying instead on rules of thumb, traditions, basic observations, and mysticism to fill in the gaps.
To the alchemist, there is no compelling reason to separate the chemical (material) dimension from the interpretive, symbolic or philosophical one. So alchemical symbols and processes often have both an inner meaning referring to the spiritual development of the practitioner as well as a material meaning connected to physical transformation of matter.
The transmutation of base metals into gold symbolized an endeavour toward perfection or the highest heights of actual existence, and the division of the world into four basic elements was as much a geometric principle as a geological one. The alchemists believed that the whole universe was tending towards a state of perfection; and gold, due to its immunity to decay, was considered to be the most perfect of substances. By attempting to transmute base metals into gold, they were, in effect, trying to give the universe a helping hand. It was also logical to think that understanding the secret of gold’s immutability might provide the key to ward off disease and organic decay; hence the intertwining of chemical, spiritual and astrological themes that was characteristic of medieval alchemy.
There is some doubt concerning the earliest mention of alchemy; it might have been in the Chinese edict of 144 B.C. or a book written in Egypt around 200 B.C. but the main line of development of alchemy began in Hellenistic Egypt, and particularly in Alexandria. 
Up to the 18th century, alchemy was considered serious science in Europe; for instance, Isaac Newton devoted a great time to the Art. Other eminent alchemists of the Western world are Roger Bacon, Thomas Aquinas, Tycho Brahe, and Thomas Browne. The decline of alchemy began in the 18th century with the birth of modern chemistry, which provided more precise and reliable framework for matter transmutations and medicine, within a new grand design of the universe based on rational materialism.
The old matter transmutation ideal of alchemy enjoyed a moment in the sun in the 20th century when physicists were able to convert lead atoms into gold atoms via a nuclear reaction. However, the new gold atoms, being unstable isotopes, lasted for under five seconds before they broke apart. More recently, reports of table-top element transmutation — by means of electrolysis or sonic cavitation — were the pivot of the cold fusion controversy of 1989. Unfortunately, none of those claims could be reliably duplicated. In either case, the required conditions were well beyond the reach of the old alchemists.
Alchemical symbolism has been occasionally used in the 20th century by psychologists and philosophers. Carl Jung re-examined alchemical symbolism and theory and began to show the inner meaning of alchemical work as a spiritual path. Alchemical philosophy, symbols and methods have enjoyed something of a renaissance in post-modern contexts, such as the New Age movement. Even some physicists have played with alchemical ideas in books such as The Tao of Physics and The Dancing Wu Li Masters.
The history of alchemy, has become a vigorous academic field. As the obscure — hermetic, of course — language of the alchemists is gradually being “deciphered”, historians are becoming more aware of the intellectual connections between that discipline and other facets of Western cultural history, such as the Rosicrucian society and other mystic societies, witchcraft, and of course the evolution of science and philosophy.
Alchemy in Ancient Egypt
Western alchemists generally traced the origin of their art to Ancient (Pharaonic) Egypt. Metallurgy and mysticism were inexorably tied together in the ancient world, as the transformation of drab ore into shining metal must have seemed to be an act of magic governed by mysterious rules. It is claimed therefore that Alchemy in Ancient Egypt was the domain of the priestly class.
The city of Alexandria in Egypt was a center of alchemical knowledge, and retained its preeminence even after the decline of ancient Egyptian culture, through most of the Greek and Roman periods. Unfortunately, practically no original Egyptian documents on alchemy have survived. Those writings, if they existed, were likely lost when the emperor Diocletian ordered the burning of alchemical books after suppressing a revolt in Alexandria (296), which had been a center of Egyptian alchemy. Egyptian alchemy is known mostly through the writings of ancient Greek philosophers, which in turn have often survived only in Islamic translations.
Legend has it that the founder of Egyptian alchemy was the god Thoth, called Hermes-Thoth or Thrice-Great Hermes (Hermes Trismegistus) by the Greek. According to legend, he wrote what were called the forty-two Books of Knowledge, covering all fields of knowledge — including alchemy. Hermes’s symbol was the caduceus or serpent-staff, which became one of many of alchemy’s principal symbols. The “Emerald Tablet” or Hermetica of Thrice-Greatest Hermes, which is known only through Greek and Arabic translations, is generally understood to form the basis for Western alchemical philosophy and practice, called the hermetic philosophy by its early practitioners.
The first point of the “Emerald Tablet” tells the purpose of hermetical science: “in truth certainly and without doubt, whatever is below is like that which is above, and whatever is above is like that which is below, to accomplish the miracles of one thing.” (Burckhardt, p. 196-7). This is the macrocosm-microcosm belief central to the hermetic philosophy. In other words, the human body (the microcosm) is affected by the exterior world (the macrocosm), which includes the heavens through astrology, and the earth through the elements. (Burckhardt,p. 34-42)
Alchemy in Ancient Greek world
The Greeks appropriated the hermetical beliefs of the Egyptians and melded with them the philosophies of Pythagoreanism, ionianism, and gnosticism. Pythagorean philosophy is, essentially, the belief that numbers rule the universe, originating from the observations of sound, stars, and geometric shapes like triangles, or anything from which a ratio could be derived. Ionian thought was based on the belief that the universe could be explained through concentration on natural phenomena; this philosophy is believed to have originated with Thales and his pupil Anaximander, and later developed by Plato and Aristotle, whose works came to be an integral part of alchemy. According to this belief, the universe can be described by a few unified natural laws that can be determined only through careful, thorough, and exacting philosophical explorations. The third component introduced to hermetical philosophy by the Greeks was gnosticism, a belief prevalent in the pre-Christian and early post-Christian Roman empire, that the world is imperfect because it was created in a flawed manner, and that learning about the nature of spiritual matter would lead to salvation. They further believed that God did not “create” the universe in the classic sense, but that the universe was created “from” him, but was corrupted in the process (rather than becoming corrupted by the transgressions of Adam and Eve, i.e. original sin). According to Gnostic belief, by worshipping the cosmos, nature, or the creatures of the world, one worships the True God. Gnostics do not seek salvation from sin, but instead seek to escape ignorance, believing that sin is merely a consequence of ignorance. Platonic and neo-Platonic theories about universals and the omnipotence of God were also absorbed.
One very important concept introduced at this time, originated by Empedocles and developed by Aristotle, was that all things in the universe were formed from only four elements: earth, air, water, and fire. According to Aristotle, each element had a sphere to which it belonged and to which it would return if left undisturbed. (Lindsay, p. 16)
The four elements of the Greek were mostly qualitative aspects of matter, not quantitative, as our modern elements are. “…True alchemy never regarded earth, air, water, and fire as corporeal or chemical substances in the present-day sense of the word. The four elements are simply the primary, and most general, qualities by means of which the amorphous and purely quantitative substance of all bodies first reveals itself in differentiated form.” (Hitchcock, p. 66) Later alchemists extensively developed the mystical aspects of this concept.
Alchemy and Astrology
Alchemy in the Western World and other locations where it was widely practiced was (and in many cases still is) closely allied and intertwined with traditional Greek astrology; in numerous ways they were built to complement each other in the search for hidden knowledge. Traditionally, each of the seven planets in the solar system as known to the ancients was associated with, held dominion over, and ruled a certain metal.
The list of rulership is as follows:
The Sun rules Gold
The Moon, Silver
Mercury, Mercury (element)|Mercury
Uranus with Uranium
As Isaac Newton was a well known alchemist of his time period, and astrology and alchemy were (and in some cases still are) so closely linked, it is very plausible that Newton had a very good working knowledge of astrology, or at the very least a basic understanding of astrological methodology as it was related to alchemy. Logically then, one would certainly have to know a good bit about astrology in order to use alchemy effectively, and Newton along with other prominent alchemists definitely knew this.
Alchemy and Psychology
Alchemical symbolism has been important in depth and analytical psychology and was revived and popularized from near extinction by the Swiss psychologist Carl Gustav Jung. Initially confounded and at odds with alchemy and its images, after being given a copy of the translation of The Secret of the Golden Flower, a Chinese alchemical text, by his friend Richard Wilhelm, Jung discovered a direct correlation or parallels between the symbolic images in the alchemical drawings and the inner, symbolic images coming up in dreams, visions or imaginations during the psychic processes of transformation occurring in his patients. A process, which he called “process of individuation”. He regarded the alchemical images as symbols expressing aspects of this “process of individuation” of which the creation of the gold or lapis within were symbols for its origin and goal. Together with his alchemical mystica soror, Jungian Swiss analyst Marie-Louise von Franz, Jung began collecting all the old alchemical texts available, compiled a lexicon of key phrases with cross-references and pored over them. The volumes of work he wrote brought new light into understanding the art of transubstantiation and renewed alchemy’s popularity as a symbolic process of coming into wholeness as a human being where opposites brought into contact and inner and outer, spirit and matter are reunited in the hieros gamos or divine marriage. His writings are influential in psychology and for persons who have an interest in understanding the importance of dreams, symbols and the unconscious archetypal forces (archetypes) that influence all of life.
Both von Franz and Jung have contributed greatly to the subject and work of alchemy and its continued presence in psychology as well as contemporary culture. Jung wrote volumes on alchemy and his magnum opus is Volume 14 of his Collected Works, Mysterium Coniunctionis.
Alchemy in the Modern Age and Renaissance
European alchemy continued in this way through the dawning of the Renaissance. The era also saw a flourishing of con artists who would use chemical tricks and sleight of hand to “demonstrate” the transmutation of common metals into gold, or claim to possess secret knowledge that — with a “small” initial investment — would surely lead to that goal.
The most important name in this period is Paracelsus, (Theophrastus Bombastus von Hohenheim, 1493–1541) who cast alchemy into a new form, rejecting some of the occultism that had accumulated over the years and promoting the use of observations and experiments to learn about the human body. He rejected Gnostic traditions, but kept much of the Hermetical, neo-Platonic, and Pythagorean philosophies; however, Hermetical science had so much Aristotelian theory that his rejection of Gnosticism was practically meaningless. In particular, Paracelsus rejected the magic theories of Agrippa and [[Nicholas Flamel|Flamel]. He did not think of himself as a magician, and scorned those who did. (Williams p.239-45)
Paracelsus pioneered the use of chemicals and minerals in medicine, and wrote “Many have said of Alchemy, that it is for the making of gold and silver. For me such is not the aim, but to consider only what virtue and power may lie in medicines.” (Edwardes, p.47) His hermetical views were that sickness and health in the body relied on the harmony of man the microcosm and Nature the macrocosm. He took an approach different from those before him, using this analogy not in the manner of soul-purification but in the manner that humans must have certain balances of minerals in their bodies, and that certain illnesses of the body had chemical remedies that could cure them. (Debus & Multhauf, p.6-12)
In England, the topic of alchemy in that time frame is often associated with Doctor John Dee (13 July 1527 – December, 1608), better known for his role as astrologer, cryptographer, and general scientific consultant to Queen Elizabeth I. Dee was considered an authority on the works of Roger Bacon, and was interested enough in alchemy to write a book on that subject (Monas Hieroglyphica, 1564) influenced by the Qabalah.