The quality of something which makes it precisely this being and not another. Various theories are proposed. The most common, following St. Thomas Aquinas, is to place the principle of individuality in the material component of bodily substances. Matter, then, is the basis of individuation. Others, with Duns Scotus, see it in a special "thisness," which distinguishes every single object in the created universe. For some the whole concrete being constitutes its individuality. And finally some hold that the existence of a thing, as distinct from its essence, ultimately explains the individuality of every single creature.