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2. The 17th Century: Reaction to the Dualism of Mind and Body

The history of philosophizing about the relation of body and mind since Descartes is the history of attempts to escape the Cartesian impasse. Early maneuvers of this sort, such as those of Malebranche, Spinoza, Leibniz, and the French materialists La Mettrie and Cabanis, were formulated in the context of metaphysics, in direct response to Cartesian dualism. Later views which arose in the 19th century needed to reconcile evidence from studies on the localization of cerebral function and on functional nervous disorders with prevailing theory in biology and psychology. These discussions reflected the newly accepted view that the brain serves as the organ of mind. Although these theories of mind/brain relations -- epiphenomenalism, interactionism, dual-aspect monism, and mind-stuff theory -- were formulated in the context of science, they too were oriented toward circumventing the Cartesian impasse.

[Figure 4] If the natural world is radically divided into the mental and the physical such that the physical is extended in space and the mental is not, and if the nature of causality is such that causes and effects must have a necessary connection and be of a similar type, then mind/body interactionism of the Cartesian sort is obviously untenable. Perhaps the first important attempt to deal with this contradiction in Descartes is that known as occasionalism. Although preceded and influenced by Le discernement du corps et de l'ame (1666) of Géraud de Cordemoy (d. 1684), the work of Nicolas Malebranche (1638-1715) was probably the most influential purveyor of occasionalism.

Born in Paris and educated at the Collège de La Marche and the Sorbonne, Malebranche began to read Descartes in 1664. A decade later, he published De la recherche de la vérité[4,see figure 4] in which he argued that both of Descartes' substances, mind and body, are causally ineffective. God is the one and only true cause. Not only is there no influence of mind on body or of body on mind, there is no causality operative at all except insofar as God, the one true cause, intervenes to produce the regularities that occur in experience. Thus, for example, when a person wills to move a finger, that serves as the occasion for God to move the finger; when an object suddenly appears in a person's field of view, that serves as the occasion for God to produce a visual perception in the person's mind.

[Figure 5] An alternative and much more enduring attempt to respond to the Cartesian impasse was that of Benedictus de Spinoza (1632-1677) [see figure 5]. Born in Amsterdam, Spinoza spent his life as a lens grinder. A Jew who had been expelled from the synagogue for unorthodoxy, he maintained few ties to either Dutch or Jewish contemporaries and published little during his lifetime. The metaphysical masterpiece,De ethica, appeared in his Opera posthuma[5], first published in 1677.

In order to retain the notion of God as the one true cause without sacrificing the idea of causality as operative in both the mental and the physical spheres, Spinoza abandoned Descartes' two-substance view in favor of what has come to be called double-aspect theory. Double-aspect theories are based on the notion that the mental and the physical are simply different aspects of one and the same substance. For Spinoza, that single substance was God. While agreeing with Descartes that the world of consciousness and that of extension are qualitatively separate, Spinoza rejected the Cartesian view that consciousness and extension are attributes of two finite substances in favor of the notion that they are attributes of only one infinite substance. That substance, God, is the universal essence or nature of everything that exists.

The direct implication of Spinoza's view is that while mental occurrences can determine only other mental occurrences and physical motions can determine only other physical motions, mind and body nonetheless exist in pre-established coordination, since the same divine essence forms the connections within both classes and cannot be self-contradictory. In the later half of the 19th century, as we shall see, dual-aspect theories underwent a revival.

Still another alternative to Cartesian interactionism is that of psychophysical parallelism. This view retains both the dualism of mind and body and the notion of a regular correlation between mental and physical events, but avoids any assumption of causal mind/body connection, direct or indirect. Psychophysical parallelism eschews interactionism on the grounds that events so totally dissimilar as those of mind and body could not possibly affect one another. It also rejects occasionalism and dual-aspect theory on the grounds that no third entity, whatever that might be, could be responsible for such vastly different effects. Parallelists simply accept the fact that every mental event is correlated with a physical event in such a way that when one occurs, so too does the other.

Parallelism in this form is usually traced to Gottfried Wilhelm Leibniz (1646-1716). Historian, mathematician, philosopher, scientist, and diplomat, Leibniz was born and received most of his education in Leipzig. In 1676, after a period at Mainz and four years at Paris, he went to Hanover, where he spent the remainder of his life. An inveterate correspondent, contributor to scholarly journals, and creator of manuscripts, much of Leibniz' most important work was embodied in letters, published in article form, or left unpublished at his death.

In the Système nouveau de la nature (1695) and the Eclaircissement du nouveau sisteme (1696), Leibniz presented the famous articulation of psychophysical parallelism in which he adapted an occasionalist metaphor to support the view that soul and body exist in a pre-established harmony. Comparing soul and body to two clocks that agree perfectly, Leibniz argued that there are only three possible sources for this agreement. It may occur through mutual influence (interactionism), through the efforts of a skilled workman who regulates the clocks and keeps them in accord (occasionalism), or by virtue of the fact that they have been so constructed from the outset that their future harmony is assured (parallelism). Leibniz rejects interactionism because it is impossible to conceive of material particles passing from one substance to the other and occasionalism as invoking the intervention of a Deus ex machina in a natural series of events. All that remains is parallelism -- the notion that mind and body exist in a harmony that has been pre- established by God from the moment of creation.


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Wozniak, Robert H. "Mind and Body: Rene Déscartes to William James"
Bryn Mawr College, Serendip 1995
Originally published in 1992 at Bethesda, MD & Washington, DC by the National Library of Medicine and the American Psychological Association.

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