 The History of Animals characterizes itself as establishing the attributes and the differences that belong to all animals, and claims that by carrying out this inquiry we are prepared to go on to search for the causes. Indeed, he appears to suggest that a successful historia or factual inquiry will prepare us to grasp the difference between those facts that need to be explained and those that will be invoked in our explanations. In the language of the Posterior Analytics: HA establishes the fact, e.g. that all animals with lungs have windpipes, or that all cetacea have lungs and are viviparous, typically seeking to identify groups by means of discovering co-extensive differentiae with the aid of the method of  division.[5]  The proper use of division, moreover, will give clear indications of which predications are basic and which derivative. Works such as Parts of Animals or Generation of Animals, on the other hand, seek to establish the reason why—the cause—of the fact. If Aristotle is following the method described in the Analytics, these causal explanations should at the same time point us to essential definitions of what it is to be a windpipe or to be viviparous. It is a question currently much debated whether definition was, in fact, an explicit goal of HA or simply a consequence of the explanatory goal clearly identified in the above passage from HA I 6; and if so, whether definitions of animal kinds were sought, or only definitions of their attributes. As we will see, there are a number of chapter summaries in the explanatory treatises that make a point of claiming that both an explanation of why a part is found in those animals that have it, and an account of what that part is, have been provided; but one must work very hard to reconstruct any definitions of animal kinds in those treatises.  [6]