He said that there were three essential kinds of substance: a perishable, physical substance, an imperishable, physical and eternal substance, and a non-material, eternal substance. In this theory, a physical substance is one that is sensible, material, movable and capable of change, and all physical substances, by definition, are studied in the field of physics. Eternal substances do not consist of elements because elements cannot exist eternally and may not always be the same in a …show more content…
It is therefore non-physical, eternal, immovable, and unchangeable, and it is known as the unmoved mover. This means that it can move other things, but is not itself moved and is immortal. This type of substance is studied under theology and includes mathematical objects and ideas. The second substance is imperishable. It is a physical substance, but it is also eternal. Examples of this type of substance include heavenly bodies which move eternally. The first substance is the one that humans are most familiar with. It is physical and perishable, and includes every physical thing on Earth like animals, plants and objects. This substance exists as a form/matter compound. In this instance, matter is what things are made out of. It is an undifferentiated, primal element, but is not itself a thing. That is, it cannot exist on its own without form. For this reason, matter is potential, meaning it has the potential to exist if it has form. Form is the structure which gives things their essential characteristics and attributes. So, matter plus form equals substance. An example of this is a cat. This bundle of flesh, fur and bones is essentially a cat. The species ‘cat’ is an unchanging form, so no matter how hard the cat tries, it cannot be a dog. But the cat can have changeable form. That is, it can have potential form. An example of potential form is the colour of the cat. It can be white or black or ginger or pink, but it