Of God and His Creatures

In the above passage, inadvertently perhaps, St Thomas admirably hits off the real meaning of what he and Aristotle called 'contingent' events, symbebêkota. An event is 'contingent' in reference to a particular system, but (apart from the doings of free will) every event is 'necessary' in the 'general system,' on the hypothesis of that system being. The killing of a sheep by lightning (see note [3.94a])is a contingency unprovided for in ovine economy, but pre-arranged in the general system of the universe, in which general system it is an hypothetical necessity: it must be, if the system is to stand as it is.

Of God and His Creatures: 3.95