Aristotle says that the intellect ("nous"), the ability to think, has no bodily organ (in contrast with other psychological abilities, such as sense-perception and imagination). Aristotle distinguishes between two types of intellect. These are traditionally called the "passive intellect" and the "active (or agent) intellect". He says that the "active (or agent) intellect" is not mixed with the body and suggests that it can exist apart from it. In his Metaphysics book Xll, he equates the active nous with the unmoved mover, of the universe, the cosmic nous, which is an idea already present in the texts of Plato.