The illusion of ownership is a facet of much suffering of, and is caused by humans (and other sentient beings, for we are all animals) under the idea that they own things, collectively or individually. How can things external of a being be owned by it, when the being, as well as that it considers itself to own, are transient, impermanent and microscopic in the long game? Especially when we consider that this illusion causes suffering to ourselves (through loss) and others (through the opportunity to grasp that which is denied).