the doctrine of divine conservation is a dangerous one. It is not theologically dangerous, at least not in itself. From the thirteenth century onwards, and particularly with the Summa Theologiae of St. Thomas, the notion of the continuous divine sustenance of the world of created things was, if not universally accepted, a nonetheless common feature of theological orthodoxy, Christian and otherwise. Rather, the danger is philosophical in nature (although, as the history of philosophy amply shows, philosophical leaks can quickly lead to theological shipwrecks). The philosophical problem I am concerned with is not some logical incoherence at the heart of the doctrine; nor does it lie in any objections that can be raised against the arguments that, historically, have been given for the thesis that God, as a causa secundum esse, must continually act in order to conserve the world in being. The question I address—and it is a pressing one for any seventeenth-century Cartesian—is whether the doctrine of divine conservation (or divine sustenance) establishes too much. I believe that, under certain circumstances, it does, and that the ultimate ramifications of the doctrine for natural causality must be unacceptable to an orthodox Cartesian such as Louis de La Forge (1632–1666), perhaps the most strict follower of Descartes of the period, the one who was most intent on being as faithful as possible to his mentor’s thought.
The key to a proper understanding of the doctrine of divine conservation lies in the distinction between a cause that operates secundum esse and a cause that [End Page 215] operates secundum fieri. Unlike a causa secundum fieri, which brings about effects that continue to persist after the productive activity of the cause has ceased (as a house will continue to exist even after the house-builder has stopped working), a causa secundum esse must continually operate causally in order for its effects to continue to exist. The light and warmth of the sun persist only as long as the sun is actively causally generating them. With this species of causation, the cause is required not just to create the effect, but to conserve or sustain it as well. As St. Thomas puts it:
Something is said to conserve something else directly and in itself in so far as that which is conserved so depends on what is conserving it that without it [the conserving thing], it [the conserved thing] could not exist [Dicitur aliquid rem aliquam conservare per se directe, inquantum scilicet illud quod conservatur dependet a conservante ut sine eo esse non possit].
On the other hand:
Some agent is a cause of its effect only with respect to its coming to be [secundum fieri] and not directly with respect to its being [secundum esse]. . . . For a builder is the cause of a house only with respect to its coming to be, and not directly with respect to its being [Aliquod agens est causa sui effectus secundum fieri tantum et non directe secundum esse ejus. ... Aedificator enim est causa domus quantum ad ejus fieri, non autem directe ad esse ejus].1
According to the doctrine of divine conservation, the causal relationship between God and the world he created—including all the particular substances in that world—is a relationship of causalitas secundum esse.
Creatures are conserved in being by God. . . . For the being of each creature depends on God in such a way that, unless creatures are conserved in being by the operation of the divine power, they could not subsist for a moment but would be reduced to nothing [Creaturae conservantur in esse a Deo . . . dependet enim esse cujuslibet creaturae a Deo ita quod nec ad momentum subsistere possent sed in nihilum redigerentur, nisi operatione divinae virtutus conservantur in esse].2
Four centuries later, Malebranche elegantly makes this same point: “As the universe is derived from nothing, it depends to such an extent on the universal cause that, if God ceased to conserve it, it would necessarily revert to nothing. For God does not will, and indeed He cannot make, a creature independent of His volitions...