This chapter is perhaps the most pivotal in The Prince, because Machiavelli discusses the relationship of action and fortune in determining the prince's success. Machiavelli uses fortune (fortuna) in at least two senses. In Chapters 7 and 8, Machiavelli contrasts virtù with fortune in the sense of luck or the favor of powerful people. In those chapters, the contrast is between what the prince can control (his own actions) and what he cannot control (the favor of others). In this chapter, fortune refers more to prevailing circumstances and events, which are still things that the prince cannot directly control. Rather than taking the fatalistic view that all events are controlled by destiny and that it is useless to work toward a particular outcome, Machiavelli gives fortune control over only half of human actions, letting free will influence the rest. If free will did not operate, all of a prince's virtù would be for nothing.
Yet Machiavelli struggles with the problem of why one person succeeds and another fails, even though they have employed the same methods, or why totally different methods can arrive at the same outcome. To explain this, he proposes that success comes when virtù is suited to the particular situation a prince finds himself in. Machiavelli envisions fortune as a set of constantly changing circumstances in which particular actions can bring about success or failure. To describe it, he uses one of his few extended metaphors, making fortune a force of nature, like a river that seems uncontrollable, yet can be tamed and directed by human activity. If the Italian princes had made suitable preparations, the "flood" of foreign invasions would not have swept over the open and unprotected country.
