 The study of the Aristotelian categories also belongs to metaphysics insofar as the categories, or the things falling under them, are studied as beings. (If they are studied as concepts, they belong instead to the logician.) There are exactly ten categories, Scotus argues. The first and most important is the category of substance. Substances are beings in the most robust sense, since they have an independent existence: that is, they do not exist in something else. Beings in any of the other nine categories, called accidents, exist in substances. The nine categories of accidents are quantity, quality, relation, action, passion, place, time, position, and state (habitus).