Causation and the Cartesian Reduction of Motion

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Authors: William EatonWilliam Eaton, Robert HiggersonRobert Higgerson
Affiliation: Georgia Southern University
Source: Causation 1500-2000, 2008
Keywords: causation [edit]

@inbook{eaton2008c,
    author = "Eaton, William and Higgerson, Robert",
    title = {Causation and the Cartesian Reduction of Motion: God’s Role in Grinding the Gears},
    booktitle = "Causation 1500-2000",
    year = "2008"}

Synopsis

Cartesian physics has the resources to explain the nature of local motion in purely mechanical terms. What this means is that in Cartesian physics, the displacement of a body from one location to another involves nothing more than changes with respect to certain modes of extension, namely, duration and location. The mechanical philosophy of the seventeenth century sought to explain all natural phenomena in terms of matter and local motion. Though more famous today for their quantitative and experimental methods, mechanical explanations were originally championed for their superior intelligibility. A highly advertised feature of the mechanical philosophy was the ability to explain natural phenomena at deeper and deeper levels, rather than accepting explanations that ended by appealing to substantial forms or occult qualities. For example, the motions of the parts of a clock might be explained in terms of matter and local motion, while the parts of the clock themselves were explained by deeper mechanical structures. We argue that an interpretation of motion, suggested by Descartes and adopted by later Cartesians such as Louis de la Forge, can explain local motion itself in a way that is more intelligible than rival explanations that ultimately take motion as a primitive.

What makes this reduction possible is the basic Cartesian metaphysical commitment that matter is essentially passive. Cartesians, including Descartes, believed that all motion was ultimately caused by God. And in God there is no real distinction between creation and preservation. In other words, at each moment God must create the world anew or else it would cease to be. La Forge realized that this provides a simple and intelligible way to account for local motion. Since God must continually re-create each object, he must always place the object in some location. Thus local motion is really a sort of divine teleportation in which an object comes into and passes away from existence at successive locations.

We argue that La Forge’s conception of motion has all the qualities valued by the mechanical philosophers. La Forge’s explanation of the nature of local motion contains such a high degree of intelligibility that all competing accounts, especially those of the scholastics, appear quite murky and superfluous by comparison. It also provides us with the best way to bridge the apparent gap between Cartesian theological metaphysics on the one hand, and Cartesian science on the other. We shall conclude by explaining how the Cartesian mechanical reduction of motion offers an interesting solution to a particular paradox of Zeno and that the Cartesian solution should be favored on the grounds of intelligibility and relative simplicity.