21. Form and Matter
Yesodei HaTorah 4:6
The cycle in which the basic elements change is caused by the revolution of the sphere. This revolution causes the elements to combine, forming the matter from which both animate and inanimate things are made. God gives each thing its appropriate form through the lowest level of angel, the Ishim.
Yesodei HaTorah 4:7
A person will never see matter without form or form without matter. The heart of man considers the things that are found and understands that they are a combination of matter and form. It grasps that there are some things whose matter is made of a combination of the four basic elements and other things whose matter contains only one of the four. There are forms that have no matter but these cannot be perceived with physical senses, only in one's heart, the same as we know God.
Editor’s note: I am not able to explain the Rambam’s science. In Moreh Nevuchim, he is willing to disregard Talmudic dicta (3:14) and even Biblical verses (2:25) in favor of observable science when necessary. Readers are free to assume either that the Rambam was sharing the best science of his day, or that he is describing spiritual rather than physical phenomena.