MECHANICAL PHILOSOPHY.

The mechanical philosophy was a philosophy of nature, popular in the seventeenth century, that sought to explain all natural phenomena in terms of matter and motion without recourse to any kind of action at a distance (cause and effect without any physical contact). During the sixteenth and seventeenth centuries, many natural philosophers rejected Aristotelianism, which had provided the form of and foundations for natural philosophy at least since the thirteenth century. The mechanical philosophy, which was rooted in ancient Greek atomism, was one candidate for a new philosophy. Atomism was the theory that everything in the material world consists of imperceptible, solid, indivisible bits of matter—atoms—that move about in empty space. Not all mechanical philosophers were strict atomists, but they attempted to explain all natural phenomena in terms of the configurations, motions, and collisions of small, unobservable particles of matter. A central doctrine of the mechanical philosophy was the theory of primary and secondary qualities, according to which matter is really endowed with only a few primary qualities and all others (such as color, taste, or odor) are the result of the impact of the primary qualities on human sense organs. Nature was thus mechanized and most qualities were considered subjective.

Background

The mechanical philosophy derived from the views of the Greek philosopher Epicurus (341–271 b.c.e.), who sought the key to the good life. He considered the good life to be one that maximizes pleasure and minimizes pain. Epicurus believed that the greatest sources of human unhappiness, apart from bodily pain, are fear of the gods and anxiety about punishment after death. To eliminate these causes of distress, he sought to explain all natural phenomena in naturalistic terms—the chance collisions of material atoms in empty space (his version of atomism), thus eliminating the gods' interference in human lives. He claimed that the human soul is material, composed of atoms that are exceedingly small and swift. The Epicurean soul did not survive death. Thus there is no reason to fear punishment in the afterlife. Epicurus believed that the atoms have always existed and that they are infinite in number. Epicureanism, while not strictly atheistic, denied that the gods play a role in the natural or human worlds, thus ruling out any kind of divine intervention in human life or providence in the world. Because of its reputation as atheistic and materialistic, Epicureanism fell into disrepute during the Christian Middle Ages. The writings of Epicurus and his Roman disciple Lucretius (c. 96–c. 55 b.c.e.) were recovered and published during the Renaissance, which began in fourteenth-century Italy.

Following the development of heliocentric astronomy in the late sixteenth and early seventeenth centuries, many natural philosophers believed that Aristotelianism, which rests on geocentric assumptions, could no longer provide adequate foundations for natural philosophy. Among the many ancient philosophies that were recovered by Renaissance humanists, Epicurean atomism seemed particularly compatible with the spirit of the new astronomy and physics. Early advocates of the mechanical philosophy included David van Goorle (1591–1612), Sebastian Basso (fl. 1550–1600), Galileo Galilei (1564–1642), and various members of the Northumberland Circle of which Walter Warner (c. 1557–c. 1642), Thomas Harriot (1560–1621), and Nicholas Hill (c. 1570–1610) were members. Although each of these men favored some version of atomism, none of them developed a systematic philosophy. Isaac Beeckman (1588–1637), a Dutch schoolmaster, advocated a mechanical view of nature and wrote about it extensively in his private journal, which was not published until the twentieth century. Beeckman's personal influence was enormous, however, and he was instrumental in encouraging a pair of French natural philosophers, Pierre Gassendi (1592–1655) and René Descartes (1596–1650), to adopt the mechanical philosophy.

Major Advocates of the Mechanical Philosophy

Gassendi and Descartes published the first systematic and the most influential accounts of the mechanical philosophy. Their treatises spelled out the fundamental terms of the mechanical philosophy and functioned as programmatic statements, describing what such a philosophy would look like in practice. Although both men agreed that all physical phenomena should be explained in terms of matter and motion, they differed about the details.

Gassendi believed that God had created indivisible atoms and endowed them with motion. The atoms, colliding in empty space (the void), are the constituents of the physical world. In his massive Syntagma philosophicum (published posthumously in 1658; Philosophical treatise), Gassendi set out to explain all the qualities of matter and all the phenomena in the world in terms of atoms and the void. He argued for the existence of the void—a controversial claim at the time—on both conceptual and empirical grounds, appealing to recent barometric experiments of Evangelista Torricelli (1608–1647) and Blaise Pascal (1623–1662). The primary qualities of Gassendi's atoms were size, shape, and mass. He attempted to explain all the qualities of bodies—light, color, sound, taste, smell, heaviness, and lightness—in atomic terms. Among the qualities he included were the so-called occult qualities, which seemed to involve action at a distance and had generally resisted explanation in mechanical terms. After laying the foundations for his philosophy, Gassendi gave an account of the entire creation: the heavens, the inanimate world, the animate world, and the human soul.

Writing in the manner of a Renaissance humanist, Gassendi saw himself as the restorer of the philosophy of Epicurus. Deeply concerned with Epicurus's heterodox ideas, Gassendi, a Catholic priest, sought to modify ancient atomism so that it would be acceptable to seventeenth-century Christians. Accordingly, he insisted on God's creation of a finite number of atoms, on God's continuing providential relationship to the creation, on free will (both human and divine), and on the existence of an immaterial, immortal human soul that, he claimed, God infuses into each individual at the moment of conception.

Gassendi was not a materialist. He argued for the existence of an incorporeal, immortal soul and also believed in the existence of incorporeal angels and demons. In addition to the immaterial, immortal soul, Gassendi claimed that there exists a material, sensible soul, composed of very fine and swiftly moving particles. This material soul (which animals also possess) is responsible for vitality, perception, and the less abstract aspects of understanding. The material soul is transmitted from one generation to the next in the process of biological reproduction. Gassendi's ideas were brought to England by Walter Charleton (1620–1707) and popularized in France by François Bernier (1620–1688).

Although Descartes also articulated a full-fledged mechanical philosophy in his Principia philosophiae (1644; Principles of philosophy), his ideas were quite different from Epicurean atomism. Impressed by the rigor of mathematical reasoning and Galileo's mathematization of physics, Descartes wanted to develop a mathematical approach to the mechanical philosophy. In contrast to Gassendi's atomism, Descartes was a plenist, claiming that matter fills all space. He claimed tht matter is infinitely divisible, thus denying the existence of both atoms and the void. He believed that matter possesses only one primary quality, geometrical extension. This belief provided foundations for his attempted mathematization of nature. Descartes drew a sharp distinction between matter and mind, considering thinking to be the essential characteristic of the mind. Like Gassendi's doctrine of the immortal soul, Descartes's concept of mind established the boundaries of mechanization in the world.

Descartes attempted to deduce the laws of motion—the conservation of motion and the principle of inertia—from first principles. From the laws of motion, he attempted to derive mathematical laws of impact. Although these laws were inadequate, even in seventeenth-century terms, their prominent place in his system reflects their importance in a mechanical philosophy, according to which contact and impact are the only causes in the physical world. Having established the physics that he considered fundamental to his system, Descartes proceeded to give mechanical explanations of all the phenomena in the world, including cosmology, light, the qualities of material things, and even the human body.

Like Gassendi, Descartes intended his philosophy to replace Aristotelianism. He hoped that the Jesuit colleges would adopt the Principia philosophiae as a physics textbook in place of the Aristotelian texts still in use. His hopes were dashed posthumously, however, when the Roman Catholic Church condemned his book in 1662 and then placed it on the Index of prohibited books one year later, in response to his attempt to give a mechanical explanation of Real Presence (the doctrine holding that Christ is actually present in the Eucharist).

William Harvey (1578–1657), a medical practitioner and teacher, inspired Descartes's mechanical philosophy by his experimental proof of the circulation of the blood, published in Exercitationes Anatomica de Motu Cordis et Sanduinis in Animalibus (1628). Harvey's natural philosophy was actually more Aristotelian than mechanical, a point manifest in his work on embryology, in which he adopted an Aristotelian explanation of generation—epigenesis, according to which the embryo is formed from the fluids contributed by both parents in the process of reproduction. Nevertheless, impressed by Harvey's use of mechanical analogies to describe the flow of blood, Descartes attempted to develop a complete physiology based on his own mechanical principles. Gassendi was not convinced by Harvey's evidence and rejected the circulation of the blood.

Another mechanical philosopher, Thomas Hobbes (1588–1679), was the specter haunting more orthodox natural philosophers. Hobbes's philosophy seemed—to the seventeenth-century reader—to be materialistic, deterministic, and possibly even atheistic. In The Elements of Philosophy (1642–1658), Hobbes propounded a complete philosophy—of matter, of man, and of the state—according to mechanistic principles. Although the details of his mechanical philosophy were not very influential among natural philosophers, his mechanical account of the human soul and his thoroughly deterministic account of the natural world alarmed the more orthodox thinkers of his day. His claims underscored their fears that the mechanical philosophy would lead to materialism, deism, and even atheism.

Later Developments

Gassendi and Descartes set the agenda for the next generation of natural philosophers, who accepted mechanical principles in general, believing that they had to choose between Gassendi's atomism and Descartes's plenism. Robert Boyle (1627–1691), Christiaan Huygens (1629–1695), and Isaac Newton (1642–1727), among the most prominent natural philosophers of the second half of the seventeenth century, developed their philosophies of nature in this context.

Boyle is best known for his attempt to incorporate chemistry within a mechanical framework. His corpuscular philosophy—which remained noncommittal on the question of whether matter is infinitely divisible or composed of indivisible atoms—was founded on a mechanical conception of matter. His reluctance to commit himself about the ultimate nature of matter reflected his concern about the atheism still associated with Epicureanism as well as his recognition that some questions lie beyond the ability of human reason to resolve. Material bodies are, according to Boyle, composed of extremely small particles, which combine to form clusters of various sizes and configurations. The configurations, motions, and collisions of these clusters produce secondary qualities, including the chemical properties of matter. Boyle conducted many observations and experiments aiming to demonstrate that various chemical properties can be explained mechanically. He performed an extensive series of experiments with the newly fabricated air pump to prove that the properties of air—most notably its "spring"—could be explained in mechanical terms.

Huygens followed Descartes in attempting to mathematize physics and the mechanical philosophy. He applied this approach to create a wave theory of light, a mathematical analysis of centrifugal force, and an improved theory of impact. He applied mathematics to physical problems far more successfully than had Descartes.

Newton, whose reputation rests on his achievements in mathematical physics and optics, accepted the mechanical philosophy from his student days at Cambridge University. A notebook written in the mid-1660s shows him thinking about natural phenomena in mechanical terms and designing thought experiments for choosing between Cartesian and Gassendist explanations of particular phenomena. A number of phenomena—including gravitation, the reflection and refraction of light, surface tension, capillary action, and certain chemical reactions—persistently resisted explanation in purely mechanical terms. Failing in the attempt to explain them by appeal to hypotheses about submicroscopic "aethers," Newton was led to the view that there exist attractive and repulsive forces between the particles composing bodies. This idea came to him from his alchemical studies. Newton's most notable discovery, the principle of universal gravitation, which provided a unified foundation for both terrestrial and celestial mechanics and which marks the culmination of developments started by Nicolaus Copernicus in the mid-sixteenth century, demanded a concept of attractive force. The concept of force, which seemed to some contemporaries to be a return to older theories of action at a distance that had been banished by the mechanical philosophy, enabled Newton to accomplish his stunning mathematization of physics and thereby fulfill the primary goal of the mechanical philosophy.

In the decades after Newton's death, the worst fears of the Christian mechanical philosophers of the seventeenth century came true. John Locke (1632–1704) argued for the reasonableness of Christianity, and his environmentalist analysis of the human mind—which grew directly from the ideas of the mechanical philosophers—implied the denial of the Christian doctrine of original sin. Deism and natural religion flourished both in England and on the Continent.

Debates about theories of generation became inextricably connected to philosophical and theological implications of the mechanical philosophy. While advocates of epigenesis tended to adopt vitalistic theories of life, theories that invoked some kind of nonmechanical entity to explain the properties of living things, another theory of generation, known as preformationism, seemed to be more compatible with the mechanical philosophy. Preformationism maintained that all living things existed within their ancestors, created by God at the beginning of life with a precise moment established for each one to emerge and become alive. Although preformationism was compatible with both divine providence and the doctrine of original sin, it also raised the specter of materialism that haunted the mechanical philosophy.

Some of the French philosophes, notably Julien Offroy de La Mettrie (1709–1751) and Paul-Henri-Dietrich d'Holbach (1723–1789), espoused atheistic materialism and also adopted vigorously anticlerical and antiecclesiastical views. David Hume (1711–1776) undermined the possibility of natural religion and a providential understanding of the world by demonstrating the invalidity of the standard arguments for the existence of God, particularly the argument from design that had played such a crucial role for the seventeenth-century mechanical philosophers. Newtonian mechanics rose to great heights, having shed the theological preoccupations of its creator. These developments culminated in the work of Pierre Simon Laplace (1749–1827), who articulated a clear statement of classical determinism and was able to demonstrate that the solar system is a gravitationally stable Newtonian system. When asked by Napoléon Bonaparte what role God played in his system, Laplace is reputed to have replied, "I have no need for that hypothesis."

See also Aristotelianism ; Cartesianism ; Humanism ; Newtonianism .

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Margaret J. Osler