DISCOURSE IV.

ON THE NATURE AND PROPERTIES

OF THE AETHER.

Since in the preceding discourse we dealt with the sublunary elements and their properties as much as seemed sufficient for our purpose, it remains now to discuss a few things concerning the Aether, or Celestial body. However, we do not here accept "Aether" as that which Aristotle calls the "fifth essence" original: "quintam essentiam", but rather as that most subtle, all-penetrating substance which, like a spirit, permeates and gives life to the whole world.

This substance, which some call the Spirit of the World, others Light, and others Innate Heat, is not a coarse or dense body, but one that is very fine and almost incorporeal. We conclude this from the fact that it penetrates even the most solid bodies—such as gold, iron, and stones—without any difficulty. If it were dense, it would certainly hinder its own movement within these bodies and would not pass through them so easily.

Properties of the Aether.

Furthermore, the properties of the Aether are many and admirable. The first is that it is the most agile of all bodies, endowed with the swiftest motion. The second is that it is the source and origin of all heat and light in the world. The third is that it is the vehicle of the spirits and faculties that operate within living bodies. The fourth is that it is the medium through which visible and audible species are conveyed to our senses.

The action of the Aether.

Not only this, but experience confirms that the Aether holds the primary role in the generation and corruption corruption: the process of decay or decomposition of natural things. For without the heat of the Aether, plants do not grow, nor are animals generated. It is the Aether that warms the seeds in the earth and brings them to maturity; it is the Aether that maintains the vital spirit in animals and excites the motion of the heart.

Finally, if anyone wishes to understand the Aether thoroughly, they must use not only philosophical reasoning but also chemical experiments. For through the chemical art, the Aether that lies hidden within bodies can be extracted and converted to human use. Indeed, if this is done correctly, it can cure diseases and prolong life.