 The closing section of PA I (treated since the Renaissance as its fifth chapter) is often thought of as having two, essentially unrelated parts. And there is some justification for this; if one were to remove the first half of the chapter, one would be left with an argument the flows quite naturally out of the conclusion of chapter 4. At that point, Aristotle states that once one has made an initial division of the attributes that belong to all the animals per se, the next step is to attempt “to divide their causes,” after which he applies the analysis of sameness and difference from the previous discussion of parts to the activities performed by these parts. He then closes the discussion by arguing that the differences we find in animal parts are to be explained by reference to differences found among their activities. Thus a proper division of activities is a division of the causes of the parts of animals.