This chapter examines the views of ancient philosophers on the connection between humans and animals. It explains the preoccupation of ancient Greeks in investigating whether the relationship between human and non-human animals involves more analogy than polarity and more sameness than differentness, and on what grounds such a determination is to be made. It discusses the pre-philosophical musings in the epic poems of Homer and analyses the philosophical views of different philosophers including the Presocratics, the Sophists, Plato and his followers, Aristotle, Theophrastus, the followers of Epicurus, and the Stoics. This chapter highlights the fact that most of these philosophers almost never composed entire treatises devoted to animals, with the exception of Aristotle and Theophrastus.