From the introduction:
The magic system presented here represents the pseudo-scientific approach of a mythical medieval alchemy. Many GMs running games in pseudo-medieval European settings will find this system adequate for their uses with little modification.
The world this system is designed for is similar to a mythical medieval Europe. The typical sorcerer sees magic as a scientific force to be manipulated through scientific (to him) means. He divides the world into four basic realms - solids, liquids, gases, and energy - which he calls earth, water, air, and fire. All things are made up of one or more of these elements. (A man's flesh is made of earth, his blood of water, his breath of air, and his spirit of fire.) He divides living things into three different realms as well - body, mind, and spirit. This world-view governs the way a sorcerer approaches magic.
Note the original version of this system was published in A Magical Medley (Fudge).