Witches were people who were supposed to make an unlawful use of the powers of life; alchemists were often thought to pass beyond what is permitted to the creature, and to encroach on the prerogative of the Creator.
The long duration of alchemy shows that it appealed to some deep-seated want of human beings.

Was not that want the necessity for the realisation of order in the universe?
Men were unwilling to wait until patient examination of the facts of their own nature, and the facts of nature outside themselves, might lead them to the realisation of the interdependence of all things.

They found it easier to evolve a scheme of things from a superficial glance at themselves and their surroundings; naturally they adopted the easier plan.

Alchemy was a part of the plan of nature produced by this method.

The extraordinary dominancy of such a scheme is testified to by the continued belief in alchemy, although the one experiment, which seems to us to be the crucial experiment of the system, was never accomplished.