Fortune and Virtu
Machiavelli's framework for understanding the interplay between luck, circumstance, and human capability in politics.
Fortuna: The River
Machiavelli used the metaphor of a flooding river for fortune (fortuna). When the river floods, it destroys everything in its path. But when the weather is calm, people can build dikes and channels to control the water. Fortune, he argued, 'shows her power where there is no organized virtu to resist her.'
He estimated that fortune governs roughly half of human affairs, leaving the other half to free will and skill. This was a radical middle position: against those who believed everything was determined by God or fate, and against those who believed human will alone could control outcomes. The political world is shaped by both forces — luck and preparation, circumstance and capability.