  Because motion or change (kinêsis) is mentioned in the  definition of nature, any discussion of nature will need to rely  upon the explanation of motion. One  might—erroneously—think that this is an easy task, because Aristotle’s  categories (as listed in the  Categories and also elsewhere) do  contain two related types of entities, action and passion.  Aristotle’s discussion of motion in the  Physics, however, starts out in a somewhat different manner.  When he submits that there is no motion besides the categories  (Physics 3.1, at 200b32–201a3), he does not assign motions to  the categories of action and passion. After mentioning that the entities  in the categories come in oppositions, Aristotle claims a few lines  later (at 201a8–9) that there are as many kinds of motion and change as  there are kinds of being. This means that motions are grouped here with  the entities of the category where they effect  change.[9]