 Aristotle’s reply is that the opponent is expected to explain why the teeth regularly grow in the way they do: sharp teeth in the front and broad molars in the back of the mouth. Moreover, since this dental arrangement is suitable for biting and chewing the food that the animal takes in, the opponent is expected to explain the regular connection between the needs of the animal and the formation of its teeth. Either there is a real causal connection between the formation of the teeth and the needs of the animal, or there is no real causal connection and it just so happens that the way the teeth grow is good for the animal. In this second case it is just a coincidence that the teeth grow in a way that it is good for the animal. But this does not explain the regularity of the connection. Where there is regularity there is also a call for an explanation, and coincidence is no explanation at all. In other words, to say that the teeth grow as they do by material necessity and this is good for the animal by coincidence is to leave unexplained the regular connection between the growth of the teeth and the needs of the animal. Aristotle offers final causality as his explanation for this regular connection: the teeth grow in the way they do for biting and chewing food and this is good for the animal. (See Code 1997: 127–134.)