Mechanism versus Aristotelianism
- Key People:
- Donald Davidson
Cartesian mechanism was opposed to scholastic Aristotelian science, which was supported by both Roman Catholic and Protestant theologians. These thinkers held that, because all things are created by God with a given nature, there can be no evolutionary development of animals or of the universe as a whole. For Aristotle, all living things possess a spirit or “soul,” which is the form, or organizing principle, of the matter out of which the organism is composed, as well as the source of its powers of growth and development, nutrition, perception, and (in humans) cognition. The soul is the essence, or nature, of the organism and its final cause—i.e., its purpose, or goal. Thus, the development of an acorn into an oak tree is explained by the fact that the acorn possesses a form that directs it toward this end.
Descartes rejected both the teleological, animistic view and the related theory of alchemy that there are vital forces in things. Cartesians denied the existence of what they considered occult or magical forces, insisting instead that only God and humans have spirits, wills, purposes, and ends. They conceived both animate and inanimate bodies as having no goals but as simply being pushed around passively. For Cartesians, science therefore consisted of looking not for final causes but rather for the laws that govern the motions of bodies.
By insisting on human free will, Descartes placed the human soul or mind, like God, outside deterministic nature. Because the body is a part of nature, however, the mind’s evident ability to control the body’s movements is, on Cartesian assumptions, inexplicable and miraculous and thus inconsistent with mechanistic determinism. Ironically, in Descartes’s system this ability is itself an occult or magical force.
Mind, body, and humanity
Most Cartesians believed that the mind and body interact. When asked how this is possible, Régis gave the standard Cartesian reply: human beings experience the interaction, and God can and does make it take place, even if we cannot understand how. As for the question of how ideas represent objects, Rohault spoke for all Cartesians when he asserted that God can make ideas represent material bodies without resembling them; no further explanation is necessary. In both of these replies, the Cartesians can be seen to abdicate philosophy for mysticism and theology.
According to the Thomists (adherents of the Aristotelian philosophical and theological system developed by St. Thomas Aquinas), the soul or mind is the form of the body. Although for Aristotle the form of an object is inseparable from the matter of which it is made, the Thomists held that the human soul is a “substantial form” that is miraculously able to exist independently of matter and thus to survive the death of the body. Descartes, by contrast, contended that the notion of substantial form is contradictory, because it assumes the separate existence of something that by definition can exist only in unity with matter. For Cartesians, the mind or soul is a substance existing in itself, independently of matter; thus, they were able to explain immortality without having to rely on the dubious assumption that the soul-form is a kind of substance. This view, however, creates a serious problem concerning the ultimate nature of human beings. According to Cartesians, sensible ideas arise from the union of mind and body for the sole purpose of preserving the body by presenting harmful things as painful and beneficial things as pleasurable. Human beings learn by experience what to seek and to avoid, and the memory of these experiences is preserved in the brain. Once the body dies, however, both the need for sensible ideas and their memory traces in the brain are destroyed. All the soul knows of matter after death is the general idea of extension. Because all bodily associations and memories are eliminated, however, individual personality is lost; each human being survives death only as an impersonal soul, identical to all other bodiless souls. Like the notion that animals are mere machines, the Cartesian conclusion that the sensible manifestations of this life are neither continued nor remembered in the next was unpopular.
Science and religion
In addition to the dualism of mind and matter in Cartesian metaphysics, there is a more general dualism in Cartesianism as a whole between a rationalist metaphysics and epistemology, which entails the existence of innate ideas of mind, matter, and God and the possibility of obtaining certain knowledge through reason, and an empiricist (and mechanistic) physics, according to which scientific knowledge, which is never certain, is gradually accumulated through observation and experience of the material world. Descartes’s insistence on the possibility of certain knowledge of God’s existence has led some commentators to present him primarily as an apologist for Christianity. Others, however, have argued that he was really an atheist and a materialist who made arguments for God’s existence only to protect himself from persecution by the church.
Although Descartes publicly denied an interest in theology, in letters he offered mechanistic explanations of transubstantiation. According to the Thomistic account of this mystery, the forms of bread and wine are miraculously sustained as substantial forms while their matter is replaced by Christ’s flesh and blood. Rohault appealed to the Cartesian view that sensible ideas are caused by configurations of the parts of material bodies to argue that, if bread and wine were replaced by flesh and blood whose parts had exactly the same configurations, the flesh and blood would look, feel, and taste like bread and wine. Although Rohault’s account still requires the miraculous replacement of bread and wine by flesh and blood, it does not rely on the self-contradictory notion of substantial form.
A deterministic Cartesian ethics was developed by the Flemish Calvinist philosopher Arnold Geulincx (1624–69). In his view, although one can do only what God has willed, one is free to accept what one must do willingly or unwillingly. Virtue consists in the humble, diligent, and obedient acceptance of the justice of God’s decrees in the light of reason, whereas sin and evil result from an egotistic (and futile) stand against God. This Stoic ethics, with its affinity to Calvinist and Jansenist predestinarianism, is as deterministic as Cartesian physics. It does, however, contradict Descartes’s claim that the human will is free not just to accept or reject the rightness of predetermined bodily actions but also to choose and cause particular actions.
Malebranche and occasionalism
The most important philosophical work stemming directly from Descartes’s writings is The Search After Truth (1674–75), by Malebranche. His position, known as occasionalism, was adopted also by Geulincx and the French philosopher Géraud de Cordemoy. Malebranche was convinced by the argument—urged most strongly by the French skeptic Simon Foucher—that, because they are so radically different, Cartesian mind and matter cannot interact. Malebranche held that, on every occasion when human bodies interact with the world, God provides the appropriate sensible ideas in human minds. And, on every occasion when human minds will that their bodies move, God makes them move. Thus, there is no direct causal interaction between mind and body; there are only separate but parallel sequences of mental and material events intermediated by God.
Foucher also argued that, because sensible ideas cannot resemble material things, they cannot represent them either, and they thus cannot be a source of knowledge of the material world. In other words, because sensible ideas such as colours, tactile feelings, sounds, odours, and tastes—as they are experienced by the mind—are utterly unlike the properties of material bodies, which are limited to size, shape, position, and motion or rest, it follows that these ideas cannot give knowledge of the material world as it really is. In response, Malebranche, like Descartes before him, simply denied that ideas must resemble their objects to represent them. Regarding the possibility that one might have sensible ideas of a nonexistent world, Malebranche said tersely that the first chapter of Genesis assures the existence of the material world. As to how human ideas of this world are true, Malebranche offered the Platonic view that ideas of all things reside in God and that, on appropriate occasions, God illuminates these ideas for human observation. Thus, human beings see all things in God and can rest assured in his goodness.
Despite Descartes’s influence on his thought, Malebranche denied that he was a Cartesian. Unlike Descartes, he argued that introspection gives no knowledge of the essence of the mind. This view prompted the English empiricist philosopher John Locke (1632–1704) to suggest that, for all human beings know, matter might be able to think. All Cartesians opposed this possibility, however, because the essential difference between mind or soul and body supports the Christian doctrine that the human soul survives the body’s death.
Later philosophers
The rationalist metaphysics of the Dutch-Jewish philosopher Benedict de Spinoza derives from Descartes. Spinoza wrote his Ethics (1677) in mathematico-deductive form, with definitions, axioms, and derived theorems. His metaphysics, which is simultaneously monistic, pantheistic, and deistic, holds that there is only one substance, that this one substance is God, and that God is the same as the world. The one substance has an infinite number of attributes, each of which expresses the totality of the world (or God), though the only attributes known to human beings are mind and matter. All attributes are parallel in every respect; that is, for every idea expressed in the mental attribute, there is a parallel body in the material attribute, and vice versa. Thus, though mind and matter do not interact, for Spinoza as for Malebranche they appear to do so.
The other great figure of late 17th-century rationalism, Leibniz, also gave a parallelistic answer to the problem of mind-body interaction. Leibniz asserted that the universe is constituted of an infinite number of simple, indivisible, extensionless substances, which he called “monads.” Each monad reflects, or perceives, the entire universe from its own point of view. Although monads do not causally interact with each other, a “preestablished harmony” between them, created and maintained by God, ensures that the appearance of interaction is maintained at the level of material objects.
The Irish radical empiricist and bishop George Berkeley (1685–1753) developed another monistic metaphysical system. Berkeley managed to avoid the problem of mind-body interaction by taking the extreme step of denying the existence of matter. Bodies, according to him, are only collections of sensible ideas that are presented to the human mind in lawful order by God. Because there is no material world, there is also no skeptical problem about whether ideas truly represent physical reality. Instead, all ideas are known directly.
By contrast, the English materialist philosopher Thomas Hobbes (1588–1679) did away with mind as a mental substance by asserting that only matter exists. For Hobbes, the mind is the same as the brain, and thoughts or ideas consist of nothing more than motions of brain matter. Because the mind is material, it is capable of causing bodily motions in response to sensory stimuli; and because ideas are material, they can resemble, and thus represent, material bodies.
