History of Animals
In the "History of Animals", Aristotle sets out to investigate the existing facts (Greek "hoti", what), prior to establishing their causes (Greek "dioti", why). The book is thus a defence of his method of investigating zoology. Aristotle investigates four types of differences between animals: differences in particular body parts (Books I to IV); differences in ways of life and types of activity (Books V, VI, VII and IX); and differences in specific characters (Book VIII).