Revival of Corpuscular Theories During the Seventeenth Century
Revival of Corpuscular Theories During the Seventeenth Century
During the seventeenth century Scientific Revolution, the Aristotelian theory of substance which had dominated European thought for 2,000 years was progressively abandoned in favor of various "corpuscular" or particulate matter theories. While foreshadowing the classical and modern atomic theories of the nineteenth and twentieth centuries, not all corpuscular theories were atomic in nature, and various ones differed on key points. Whereas some were inspired by ideas drawn from the ancient Greek atomists, others developed out of Western and Islamic medieval matter theories. All of them, however, fundamentally challenged previously accepted notions of matter, motion, space, and substance in physics and chemistry, and generated intense philosophical and religious controversies as well.
Western culture inherited two major philosophical theories about matter and motion from ancient Greece. Leucippus (fl. fifth century b.c.) and Democritus (c. 460-370 b.c.) argued that the world consists of minute, indivisible bits of matter (atomos means indivisible). Atoms are eternal, uncreated, and indestructible, infinite in number, and in constant motion through void space; their only properties are size, shape, and solidity. All objects and their qualities—color, taste, texture, etc.—and changes in these result from the motion, collision, combination, and separation of atoms. Combinations of atoms can vary in quantity, shape (H or V), order (HV or VH), or position (V). All atomic motions occur due to strict necessity or fate, rather than chance or free will. Later, Epicurus (c. 341-270 b.c.) and his disciple the Roman poet Lucretius (c. 99-55 b.c.) modified these views by introducing the concepts of relative weight for different types of atoms and of an indeterminate swerve in atomic motions.
Against atomism, Aristotle (384-322 b.c.) pitted his hierarchical theory of qualities, elements, and substances. In the sublunary realm, four primary qualities—hot, cold, wet, dry—combine in complementary pairs to "inform" or determine a completely qualityless, indeterminate substrate of "prime matter"—fire = hot + dry, air = hot + wet, water = cold + wet, earth = cold + dry. All four elements are in turn combined in various proportions to form the homoiomere, or materially uniform, tangible substances (e.g., granite, iron, blood, bone) that are the basic physical constituents of the world. These homoiomere in turn combine to constitute anhomoiomere, or complex, higher-order parts and organisms (e.g., petals, hands, plants, human beings), which are also substances. (Whether Aristotle himself believed in prime matter, and also considered the four elements to be substances, or only was interpreted as doing so by later commentators, is now a much-debated topic.)
For Aristotle, a substance is a unitary entity having an essence, or unique and irreducible set of defining activities and properties, and a nature, or innate principle that determines and directs these. Each physical substance is a complex unity of a single form and its matter, which respectively manifest its actuality, or characteristic pattern of activity, and potentiality, or latent capacities for alternative actualities. All real changes involve substances, and consist of two types—essential (substantial) change, in which one substance becomes another substance (e.g., a caterpillar becomes a butterfly), and accidental change, in which a substance alters in size, place, or quality, while its essence remains the same (e.g., John Smith grows taller, sits down, or his hair changes from black to gray, but he still remains John Smith). Aristotle also rejected the existence of void space in favor of a concept of place as positional relations between physical objects. Finally, he distinguished four principles or causes of change—formal, material, efficient, and final—which explain not just how a substance changes but also why, offering not just a mechanism for change but a purpose and goal for it as well.
The theories of the atomists and of Aristotle were thus profoundly opposed in several ways. The atomist universe was constructed from the bottom up, out of atoms as the basic real units of the physical world. All tangible objects and their qualities are merely accidental, phenomenal aggregates of atoms, governed by necessity or chance, without an essential unity of structure, function, or purpose to guide and perpetuate their existence. Aristotle's cosmos was organized from the top down, with substances and qualities as the fundamental real entities of the physical world. The elements are conceptual constitutive principles which do not exist separately, but only in combination with one another. As essential unities, substances are structured, organized objects, whose inherent natures perpetuate their existence and direct their activities toward the realization of specific goals, thereby allowing for the existence of reason and free will in man.
Aristotle's system quickly triumphed over the atomists' ideas for several reasons. First, it more convincingly explained many natural properties and activities, especially biological ones. Second, its emphasis on essential structure and function, instead of merely accidental phenomena, attributed a sense of order to the universe that made it more explicable. Third, its provisions for purpose and free will, instead of chance or determinism, were more compatible with belief in God and personal moral responsibility, whereas Epicureanism gained a reputation for atheism and immorality (hedonism). With the subsequent rise of Christianity in Western culture and the adaptation of Aristotelian philosophy in support of Christian theology, atomism remained out of favor for over 1,500 years. Lucretius's poem De Rerum Natura, the only atomist text from antiquity to survive intact, would not be recovered by Western Europe until 1417.
By the late sixteenth century, severe difficulties with Aristotle's theories had become apparent. His generally qualitative approach proved unsuitable to newly developed quantitative and mathematical methods in physics. The doctrine of substance did not explain adequately how existing chemical substances combine to form new substances, or why the original substances reappear upon decomposition. The Paracelsian chemical doctrine of three immaterial principles of matter challenged Aristotle's four-element theory; new astronomical discoveries undermined his distinctions in material composition and motion between the superlunary and sublunary cosmic spheres; and barometric experiments by Evangelista Torricelli (1608-1647) proved the existence of the vacuum. Particulate matter theories, however, could explain physical phenomena in quantitative rather than qualitative terms, and avoid many problematic aspects of Aristotelian substance.
Ironically, the first early modern particulate matter theories developed out of Aristotle's philosophy, not atomism. A passage in Book I.4 of Aristotle's Physics was interpreted to suggest that, while matter as such is infinitely divisible, specific substances consist of minima naturalia, or particles of a minimum natural size, whose physical division entails destruction of their substantial natures. The great Arabic commentators, Avicenna [Ibn Sina] (980-1037) and Averroës [Ibn Rushd] (1126-1198), developed this concept and modified Aristotle's theory of substance to suggest that in chemical reactions, a substantial form of the product "supervenes" upon the forms of the constituents, but the latter persist as "virtual" forms that reappear when the product decomposes. This theory was transmitted to Europe during the thirteenth century, attracting the interest of the medieval scholastics. By the sixteenth century, commentators such as Augustine Nifo (1473-1546?), Julius Caesar Scaliger (1484-1558), and Jacopo Zabarella (1532-1589) increasingly stressed the concept of minima naturalia and de-emphasized that of substance.
The revival of Epicurean atomism was due primarily to the French priest and philosopher Pierre Gassendi (1592-1655), who overcame most theological objections to atomism by recasting it to conform to Christian doctrines. Instead of being infinite in number, eternal, indestructible, and in perpetual motion, atoms are finite in number, being originally created and set into motion by God, who directs their movements according to regular laws to accomplish specific ends. Atomic matter is passive and inert; the fundamental properties of atoms are size, shape, weight, and solidity (impenetrability), with all other qualities resulting from their combinations by means of interlocking sets of hooks, points, and pores. Space exists apart from matter, as a real geometric framework that contains both material bodies and vacuums that separate them. By contrast, God made angels and human souls out of an incorporeal matter that does not constitute physical bodies or occupy space. Matter, its phenomenal modes of appearance, and space thus replaced the Aristotelian categories of substance, real qualities, and place; corporeal matter became equated with physical body and void space with the absence of body; and motion (as efficient cause alone) became the only category of real change.
While Gassendi's system was the most influential, propagated in England by Walter Charleton (1620-1707) and in continental Europe through the correspondence network of Marin Mersenne (1588-1648), it competed for decades with several rivals. Some philosophers endorsed indivisible atoms, other minima naturalia; some accepted and others rejected the existence of void space apart from matter; some believed motion was inherent in atoms, others that atoms were inert and moved by external forces. Generally, physicists favored atoms, while chemists preferred minima naturalia. Galileo Galilei (1564-1642), in formulating the laws of physical motion, treated atoms as mathematical points instead of hard bodies occupying space. René Descartes (1598-1650) equated matter with three-dimensional spatial extension, denied the existence of the void, and posited a material plenum filled by particles of three different sizes but indeterminate shapes that formed swirling vortices in constant motion. The German physician Daniel Sennert (1572-1637) proposed a compromise system, wherein atoms constituted the four Aristotelian elements, which in turn constituted the three Paracelsian principles, whose various combinations then constituted the corpuscular minima naturalia of tangible substances. The British chemist Robert Boyle (1629-1698), influenced by Charleton, adopted the term corpuscles to avoid a commitment to either atoms or minima, since neither the divisibility or indivisibility of matter could be proved by experiment.
Though conclusive proofs for corpuscular theories were lacking, advocates appealed to several types of phenomena to support their position. Processes of growth, condensation, evaporation, and abrasion were explained by accretion and dispersion of microscopic particles. So too was the composition and motion of nonmaterial species such as light, heat, sound, magnetism, and (later) electricity. Observations made after the invention of the microscope in 1661 suggested that many macroscopic objects have a particulate microscopic constitution. Ultimately, the authority of Boyle's friend, Sir Isaac Newton (1642-1727), who employed atoms in his theories of gravitation and optics, established a dualistic theory of atomic matter and immaterial forces. By separating inert atomic matter from active forces as the manifest power of God in nature, Newton (like Gassendi) sought to preserve atomism from any taint of atheism or denial of human free will, against philosophical sceptics such as Thomas Hobbes (1588-1679).
The shift from substantial to corpuscular matter theories was vital to a broader conceptual change from organic to mechanical modes of explanation. In Aristotelian philosophy the activities of inanimate objects and systems, from metallic ores to planetary motions, were explained by analogies to living organisms. Corpuscular theories reversed this pattern, so that biological and even mental processes were explained by analogies to inanimate machines. Instead of being conceived in holistic terms as complex, irreducible unities, entities were now viewed in reductionist terms as merely sums of their simpler parts. Scientific explanations became descriptive rather than purposive, asking and answering questions of "how" rather than "why" objects act as they do. A corresponding shift from qualitative to quantitative descriptive methods encouraged use of standard schemes of classification, and the formulation of universal natural laws in mathematical terms. This promoted higher standards of accuracy and precision, indispensable to the technological advances of the Industrial Revolution that have radically transformed everyday life since 1750. The "mechanization of the world picture," as one historian has termed it, reigned for two centuries, until the twentieth century revolutions in subatomic physics, astronomy, biochemistry, and ecology began to swing the pendulum back, with theories of fields, networks, and systems all being opposed to mechanistic reductionism and emphasizing organic and holistic concepts instead.
JAMES A. ALTENA
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