The traditional interpretation of Aristotle, which goes back as far as Augustine (De Genesi contra Manichaeos i 5–7) and Simplicius (On Aristotle’s Physics i 7), and is accepted by Aquinas (De Principiis Naturae §13), holds that Aristotle believes in something called “prime matter”, which is the matter of the elements, where each element is, then, a compound of this matter and a form. This prime matter is usually described as pure potentiality, just as, on the form side, the unmoved movers are said by Aristotle to be pure actuality, form without any matter (Metaphysics xii 6). What it means to call prime matter “pure potentiality” is that it is capable of taking on any form whatsoever, and thus is completely without any essential properties of its own. It exists eternally, since, if it were capable of being created or destroyed, there would have to be some even lower matter to underlie those changes. Because it is the matter of the elements, which are themselves present in all more complex bodies, it is omnipresent, and underlies not only elemental generation and destruction, but all physical changes.