What is substance according to Aristotle?
Substance is, as you rightly mentioned, a conjunction of ideal and matter, they are simple, objects themselves and not the properties possessed by those objects. Substances are things subjected to properties, and are divided into primary substances and secondary substances. This might seem a bit counter-intuitive, so here are some examples to hopefully simplify it. A primary substance would be a particular, such as a cat named Felix. You could say things about Felix, for example, Felix is black, Felix is furry, Felix has four legs, but you could never use Felix to describe something else. Felix is, therefore, a substance, but not an attribute. However, Felix is a cat, and cat itself is also a substance, that is, a kind. A ‘kind’ is the secondary substance, like a category, Felix the Cat falls in the category of Cats. So, to break it down: Felix, the Particular, is a Primary Substance. Cat, the kind, is a Secondary Substances. Basically, substances are ‘things’. Primary substances are t