A substance is an entity like an apple, an acorn, a leaf, a carbon atom, a dog, or an angel. Substances have a number of important characteristics.9 First, substances are particular, individual things. A substance, like a particular acorn, cannot be in more than one place at the same time. Second, a substance is a continuant—it can change by gaining new properties and losing old ones, yet it remains the same thing throughout the change. A leaf can go from green to red, yet the leaf itself