Responding to the claims of Parmenides on the impossibility of change, Anaxagoras described the world as a mixture of primary imperishable ingredients, where material variation was never caused by an absolute presence of a particular ingredient, but rather by its relative preponderance over the other ingredients; in his words, "each one is... most manifestly those things of which there are the most in it". He introduced the concept of "Nous" (Cosmic Mind) as an ordering force, which moved and separated out the original mixture, which was homogeneous, or nearly so.