In this book the most important aristotelian passages concerning the question of determinism are thoroughly reexamined: chapter 9 of de interpretatione, chapter 3 of Metaphysics's book VI, several chapters from the Ethics, as well as some texts from the aristotelian commentator Alexander of Aphrodisias. This is the author's main contention: "In Aristotle's view the world of social relations and of human behaviours really is always highly undetermined; but this is mainly due to the unpredictable intersections of the different causal series issuing from each agent involved, while in each of these series at least one element tends to remain constant (indeed, it is the most stable element in every situation): the personal character of the human agent and the kind of response this character offers to the new situations that constantly arise".