This essay contributes to the discussion of the concepts of necessity, fortune, and chance. It shows the complexity of these concepts and the precariousness of the idea of necessity, an idea that is fundamental for Stoicism and Laplace’s determinism. References to Aristotle and Cournot are useful here so as to define the objectivity of chance and the unintentional and irrational character of the events concerning fortune. Thus the essay emphasizes the uncertainty of all predictions concerning the future.