In fact, they carried them much farther than we are disposed to do, extending them even to inorganic or mineral things.

The fundamental principle of alchemy was the natural process of development of metalline bodies.

"When common people," says Al-Khazini, writing in the twelfth century, "hear from natural philosophers that gold is a body which has attained to perfection of maturity, to the goal of completeness, they firmly believe that it is something which has gradually come to that perfection by passing through the forms of all other metallic bodies, so that its gold nature was originally lead, afterward it became tin, then brass, then silver, and finally reached the development of gold; not knowing that the natural philosophers mean, in saying this, only something like what they mean when they speak of man, and attribute to him a completeness and equilibrium in nature and constitution--not that man was once a bull, and was changed into an ass, and afterward into a horse, and after that into an ape, and finally became a man.".