DISCOURSE IV.

ON THE NATURE AND PROPERTIES OF THE ELEMENTS.

Since in the preceding sections we have dealt with the natural principles of things in general, we must now deal with the elements, which are the immediate principles of mixed bodies. An element, as Aristotle defines it, is a simple body into which other bodies are resolved, and from which they are primarily composed.

I. On the Number of the Elements.

There has been great controversy among philosophers regarding the number of elements. Empedocles established four: Earth, Water, Air, and Fire. The common consensus of all and experience itself confirm this opinion. Although they do not appear in their purity within mixed bodies, yet when a resolution is made, they are ultimately resolved into these four.

II. On the Primary Qualities.

Elements differ not only in substance but also in qualities. The primary qualities are four: Hot, Cold, Moist, and Dry. These are active and passive:

• Hot and Cold are active, because they act upon matter.
• Moist and Dry are passive, because they are acted upon.