Chemistry did not emerge as a science until after the scientific
revolution in the seventeenth century and then only rather slowly and
laboriously. But chemical knowledge is as old as history, being almost entirely
concerned with the practical arts of living. Cooking is essentially a chemical
process; so is the melting of metals and the administration of drugs. This basic
chemical knowledge, which was applied in most cases as a rule of thumb
(单凭经验来做的方法), was nevertheless dependent on previous experiment. It also served
to stimulate a fundamental curiosity about the processes themselves. New in
formation was always being gained as artisans improved techniques to gain better
results. The development of a scientific approach to chemistry
was, however, hampered by several factors. The most serious problem was the vast
range of material available and the consequent difficulty of organizing it into
some system. In addition, there were social and intellectual difficulties.
Chemistry is nothing if not practical; those who practice it must use their
hands, they must have a certain practical flair (鉴别力). Yet in many ancient
civilizations, practical tasks were primarily the province of a slave
population. The thinker or philosopher stood apart from this world, where the
practical arts appeared to lack any intellectual content of interest.
The final problem for early chemical science was the element of secrecy.
Experts in specific trades had developed their own techniques and guarded their
knowledge to pre vent others from stealing their livelihood. Another factor that
contributed to secrecy way the esoteric (深奥的) nature of the knowledge of
alchemists (炼金术士). In one sense, the second of these was the more serious
impediment (阻碍) because the records of the chemical processes that early
alchemists had discovered were often written down in symbolic language
understandable to very few or in symbols that were purposely obscure.