Causality

Descartes's successors were divided into two groups: the occasionalists and those who reintroduced activity into nature. Occasionalism is the view that the only real cause of everything is God and that all causal talk that refers to worldly substances is a sham. Nicolas Malebranche (1638–1715) drew a distinction between real causes and natural causes (or occasions). As he put it: "A true cause as I understand it is one such that the mind perceives a necessary connection between it and its effect. Now the mind perceives a necessary connection between the will of an infinite being and its effect. Therefore, it is only God who is the true cause and who truly has the power to move bodies" (1997, p. 450). Natural causes are then merely the occasions on which God causes something to happen. Malebranche pushed Cartesianism to its extremes: since a body's nature is exhausted by its extension, bodies cannot have the power to move anything, and hence to cause anything to happen. What Malebranche also added was that since causality involves a necessary connection between the cause and the effect (a view that Descartes accepted too), and since no such necessary connection is perceived in cases of alleged worldly causality (where, for instance, it is said that a billiard ball causes another one to move), there is no worldly causality: all there is in the world is regular sequences of events, which strictly speaking are not causal. Gottfried Wilhelm Leibniz (1646–1716), on the other hand, aimed to reintroduce forces and active powers into nature. As he said: "activity is the essence of substance" (1981, p. 65). Each substance is sustained by an internal "primitive active force," which causes its subsequent states. Yet, in a rather puzzling move, he also thought that there is no real causality in nature, since Leibnizian substances (what he called "the monads") do not interact. Rather, they are coordinated with each other by God's act of preestablished harmony, which confers on them the natural agreement of exact clocks.

There is an irony to be noted at this point. Most early modern philosophers tried to solve the metaphysical issue of causality. They devised elaborate theories to explain how the cause brings about the effect. But in the end, they excised causality from nature. More mildly put, insofar as there was causality in nature it was taken to be the product of divine impulse (Descartes) or of mysterious primitive forces (Leibniz).