Both randomness and regularity exist in history, but in variable proportions. The settlement, empire-building, warfare, and revolutions of the Greater Caribbean involved regular patterns not clear to all participants, if surely to some. The varying valor and skill of the generals and admirals, the arc of the cannonballs as affected by the wind – these may have been random. But the outbreaks of yellow fever and malaria upon the introduction of thousands of nonimmunes into the region were regular events and highly predictable, even if puzzling, to those familiar with the region. These outbreaks were not random except in their timing, which depended mainly on the timing of new arrivals of virus-fodder, and in their severity, which depended on many things. Instead, they formed a regular pattern that constrained randomness, and severely narrowed the range of likely outcomes of the political struggles in the Greater Caribbean. The pattern did not quite determine political outcomes because highly unlikely things can always happen – Finns or Maori might somehow have conquered the whole region – but it dramatically raised the probability that the Spanish Empire in the Americas would stay Spanish until 1800 and that the revolutions fought between 1776 and 1826, and that of 1895–1898, would succeed militarily.

THE ARGUMENT RECAPITULATED

Put less philosophically, the aim in these pages has been to convince readers of the strength of the linkages between ecological and political affairs in general, and in particular of the power of yellow fever and, to a lesser extent malaria, to shape settlement, empire-building, imperial rivalries, and revolutions in the Greater Caribbean from the 1640s to the 1910s.