Early Greek Matter Theories: The Pre-Socratics to the Stoics

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Early Greek Matter Theories: The Pre-Socratics to the Stoics

Overview

Between the sixth and the third centuries b.c., the classical Greek philosophers proposed numerous theories regarding the material composition of the universe, with those of the atomists, Aristotle (384-322 b.c.), and the Stoics emerging as the major alternatives. While providing the intellectual foundations for subsequent developments in Western chemistry and physics, the primary purpose of these theories was not to offer a scientific account of nature in the modern sense, but rather to pose and answer philosophical questions regarding the structure of reality, the certainty of knowledge, and the formulation of ethical principles.

Background

Like those of other ancient civilizations, the earliest Greek cosmological theories were mythological accounts of the creation of the universe by the gods. However, in about 600 b.c. a tradition of speculative thought emerged that, while not rejecting religion, sought to offer coherent explanations in nonmythological terms. Unfortunately, the writings of the pre-Socratic philosophers and the later Stoic naturalists have all been lost. While scholars have made speculative reconstructions of their views, based on surviving isolated quotations from their works, and summaries and criticisms of their ideas by Aristotle and other commentators, many basic details remain controversial.

Despite some radical differences of opinion, the early Greek philosophers ("lovers of wisdom") all believed that the universe has a fundamental order (cosmos = order), knowable by human minds through the use of reason and sensory perception. They also assumed two initial logical principles: the law of identity (A = A) and the law of noncontradiction (A¹ ≠ not-A). Together these three principles determined the basic questions these philosophers posed about the constitution and structure of the natural order. What is the cosmos made out of? How is it structured? Is it eternal, or does it have a beginning and an end? How are different objects and events identified, distinguished, and related to one another? Are space, time, and material objects real, or merely subjective perceptions?

These questions sought to address two major problems. The first of these is termed the One and the Many. If the cosmos is One, or a unity, then how do different objects and events arise? But if it consists of many things, how can it have any unity and structure? The second and related problem is that of Continuity and Change. If an object or event is itself, and cannot be something it is not, then why and how do things appear to change into other things? If change is real, then how can anything have a permanent and distinct identity? How can anyone know for sure what a thing is, if it is subject to change? How is reality distinguished from mere appearance, and the permanent from the temporary?

The earliest Greek philosophers were all monists who believed the cosmos to be a unity constituted from a single element; however, they disagreed sharply as to its nature and identity. There is little sound information about Thales of Miletus (624?-547? b.c.), the first Western philosopher known by name, except that he asserted everything is made of water and that "all things are full of gods." He is presumed to have meant that water is a universal elemental principle, observed in gaseous, liquid, and solid forms as steam, water, and ice, whose transformations are evidence of an inherent animating power.

More is known about his successor, Anaximander (c. 610-c. 545 b.c.), though again only a single quotation survives: "Out of those things whence is the generation of existing things, into them also does their destruction take place, as is right and due; for they make retribution and pay the penalty to one another for their injustice." Anaximander held that the universe is constituted out of a single, eternal, divine material principle called the "unbounded" (apeiron), which enfolds all things. From the apeiron is engendered a primordial pair of opposites, Hot and Cold, whose interaction gives rise to the basic elemental principles (water, air, fire) and opposing powers and qualities (e.g., hot-cold, dry-wet, heavy-light, rough-smooth, bright-dark). The tension between these opposites causes the universe to undergo repeated cycles of generation and destruction, as one extreme or the other gains dominance. Anaximander also used these opposites to explain meteorological phenomena (wind, lightning, thunder), and proposed an elaborate model of the solar system.

The third Milesian philosopher, Anaximenes (fl. c. 545 b.c.), proposed air as the universal element, as shown by his only extant statement: "Just as our soul, being air, holds us together, so do breath and air surround the whole cosmos." Unlike Thales's water and Anaximander's apeiron, "air" here denotes not an abstract causal principle but the common physical substance. Air envelops and constitutes all things, even the gods and living souls. Constantly in motion, it gives rise to various natural objects and occurrences by successive stages in an ongoing process of rarefaction (generating fire) and condensation (resulting in water and earth).

The next two great monistic thinkers staked out opposing positions that influenced their successors for centuries. For Heraclitus of Ephesus (540?-480? b.c.), from whose writings about 125 cryptic epigrams survive, fire is the universal element and animating divine principle: "All things are an exchange for fire, and fire for all things." The uncreated and eternal cosmic One is process—a cyclic flux of constant change, "an ever-living fire being kindled in measures and being extinguished in measures," governed by a Logos, or material principle of Strife between yoked opposites, whose transformations or "turnings" provide continuity, stability, and balance to the whole: "Fire lives the death of earth and air lives the death of fire, water lives the death of air, earth that of water." These four elements correspond very roughly to the modern concept of energy and to the gaseous, fluid, and solid states of matter. The senses provide reliable information, but reason must interpret them, if appearances of permanence are not to deceive: "Upon those who step into the same rivers, different and again different waters flow."

For Parmenides of Elea (515?-450? b.c.), however, the cosmic One—whose nature he did not specify, though it recalls Anaximander's apeiron—is not only uncreated, eternal, continuous, and necessary, but also unchanging and unchangeable, indivisible into distinguishable parts, complete and whole in and of itself. From his argument comes the famous principle that "out of nothing, nothing comes to be." All appearances of change, including time and motion, are illusory; commonplace speech and the senses are untrustworthy; reason alone supplies true knowledge. In extant fragments of his poem On Nature—which offer the first surviving philosophical argument in Western history—Parmenides distinguishes three paths to knowledge: the right Way of Truth, the false Way of Opinion, and the misleading Way of Inquiry, which nonetheless allows the seeker to find out the Way of Truth. His pupil, Zeno of Elea (495?-430? b.c.), is still famous for his imaginative (if ultimately fallacious) paradoxes, designed to prove the impossibility of plurality, motion, change, or divisions in time and space.

The philosophical impasse created by Heraclitus and Parmenides was broken when subsequent thinkers abandoned monism and embraced pluralism as their fundamental starting principle. By assuming an initial multiplicity of cosmic elements, they obviated the question of the One and the Many by eliminating any need to explain how the latter arose out of the former. This also in part resolved the question of Continuity and Change, by allowing for the reality of both; basic elements could remain unaltered, while their various combinations did not. The most important issues thus became the identities and natures of those elements; the fundamental principles and modes of their interactions; and the nature of matter, time, space, and place. This also coincided with a shift away from models based upon astronomical phenomena toward principles drawn from biology, and a correspondingly increased emphasis upon issues of human ethics and psychology.

Impact

The first pluralist matter theory was that of Empedocles of Acragas (492?-432? b.c.). Drawing upon Heraclitus, Parmenides, and the Pythagorean principle of number as the fundamental reality of all things, Empedocles taught in his poem On the Nature of Things (Peri physikos) that fire, air, water, and earth are the four eternal and indestructible material elements or "roots" of the cosmos. Swirling in a constantly rotating vortex that constitutes a material plenum without void space, these roots constantly mix, aggregate, and separate to produce various natural objects, each composed of certain elements in characteristic proportions (e.g., bone is composed of earth, water, and fire in a ratio of 2:2:4). Combination and separation of the elements is governed by two primeval forces, Love and Strife, which alternately dominate in a fluctuating cycle of unity and diversity. Empedocles was the first philosopher to distinguish between elements, compounds, and physical mixtures; to assert that compounds are in some sense real and not just phenomenal unities; and to reject strict necessity and introduce "chance" as a causal principle of motion and change. These roots and forces also account for complex biological and psychological factors, and a cosmic religious cycle of sin and redemption.

Empedocles's contemporary Anaxagoras of Clazomenae (500?-428? b.c.) in turn took the concept of multiplicity to the farthest extreme. In his book On Nature (Physika), he taught that the cosmos is a material plenum, in which there are as many different types of uncreated and eternal original "seeds" (spermata) as there are types of "basic matter" (homoiomere). This plenum is infinitely divisible—there are no "smallest portions" of any type of matter—with seeds of every type of matter in every object: "in everything there is a portion of everything." Objects are constituted of a particular type of matter because they contain a predominant portion of those seeds in comparison to all the other types of seeds (e.g., a gold bowl is composed primarily of gold seeds). Originally all the seeds and portions were mixed together in an undifferentiated cosmic unity, but subsequently were partially segregated by the rotating cosmic vortex according to the principle of "like attracts like." This cosmic vortex is governed by "mind" (nous), an immaterial vital principle that alone is originally unmixed with other things, and which alone knows, rules, orders, and moves all things according to opposing cosmic principles (e.g., hot-cold, dry-wet, heavy-light, rough-smooth, bright-dark). Anaxagoras was the first to distinguish a moving agent from both objects moved and principles of motion.

The third and most important of the pre-Socratic matter theories was that of the atomists Leucippus of Miletus (fifth century b.c.) and his pupil Democritus of Abdera (460?-370? b.c.) The former is a shadowy figure from whom only a single quotation survives: "Nothing happens in vain, but everything from reason and necessity." While over 100 sayings of Democritus are extant, most concern his ethical teachings, with only one directly concerning his theory of atomism: "By custom sweet and by custom bitter, by custom hot, by custom cold, by custom color; but in reality atoms and void." Nevertheless, the content of their theory is well known, both from the extensive criticisms of Aristotle and its later adoption by the Hellenistic philosopher Epicurus of Samos (341-270 b.c.), a few details of which survive in his Letter to Herodotus. Subsequently the Roman poet Titus Lucretius Carus (99?-55 b.c.), in his classic work On the Nature of Things (De rerum natura), preserved many otherwise lost details of Epicurus's doctrine; it is the only surviving intact account from antiquity of a non-Aristotelian matter theory.

According to the early atomists, the infinite cosmos consists of minute, indivisible bits of matter called atomos (from the Greek for "indivisible") and void space. Atoms are eternal, uncreated, indestructible, infinite in number, and in constant motion within a vortex through the void; their only properties are size, shape, and solidity. (Whether or not atoms also had weight, and if so in what way, remains controversial.) All atomic motions occur due to strict necessity or fate, not chance or free will. Combinations of atoms may vary in quantity, shape (H or V), order (HV or VH), or position (V or L). All objects and their qualities (color, taste, texture, etc.), and changes in these, are merely phenomenal appearances, resulting from atomic shapes, motions, and interactions due to forces of attraction, repulsion, and cohesion. (For example, pointed atoms produce a bitter taste, and round atoms a sweet one; smooth atoms produce bright colors, rough atoms dark ones.) Objects are perceived because they radiate ephemeral atomic films or "images" (eidola) to the observer's eye or field of vision. Since the human soul is also composed of atoms, it disintegrates with death; there is no immortality, and the gods are merely giant eidola.

The atomists were the first to posit a strictly mechanical account of motion, and to distinguish between primary and secondary qualities. While atoms are in effect fragments of the Parmenidean One, the atomists broke from Parmenides not only in substituting the Many for the One, but in their crucial distinction between relative material nonexistence, called ouk on, (not being), or the void of absolute nonexistence, called ouden (nothing). Since the Greeks did not consistently distinguish place as the relative location of objects from space as the extension in place of a given object, or conceive of absolute space as a set of dimensions existing apart from any objects, the void denoted any interval between two atoms, whether separate or conjoined, not the modern concept of a vacuum.

Aristotle's criticisms of the early atomists led Epicurus and Lucretius to revise atomism in several ways. For them weight, defined as downward linear motion toward the center of a spherical cosmos, is a primary atomic property. Atoms move from place to place almost instantaneously at the same speed, rather than varying in speed by size. Space is distinguished from the void as a type of "intangible existence" and hence is also real (though Time remains an accidental property of motion). The complex bodies composed by atomic aggregates, and their qualities, are not merely phenomenal, but also real; thus in their view the senses are more reliable sources of information than for Democritus, and the soul is also a real body. Most important of all was Epicurus's novel idea of an atomic "swerve," or occasional slight random deviation in the motions of atoms. While heavily criticized by other philosophers as illogical, this doctrine sought not only to explain atomic motions and interactions (since atoms falling perpetually in straight lines would never collide), but also to reject the strict causal necessity and fatalism of early atomism and thus preserve a measure of free will and moral responsibility in human actions.

A very different version of atomism was proposed by Socrates's great pupil, Plato (427?-347 b.c.). Ignoring Democritus altogether and drawing for inspiration upon Pythagorean geometry, Plato suggested in his dialogue Timaeus that there are five different types of geometrical atoms, corresponding to the five perfect geometrical solids (having sides all of equal length, faces all of equal size and shape, and angles all of equal degree). Four of these solids correspond to the traditional four elements—fire: tetrahedron, earth: cube, air: octahedron, water: icosahedron—and the fifth (the dodecahedron) to the entire cosmic sphere. The faces of the first four solids are in turn readily divisible into either equilateral triangles (for fire, air, and water) or isosceles triangles (for earth). (As the unitary cosmic symbol, the dodecahedron does not require division.) Thus the geometric "atoms" are not indivisible, but are assembled from and disintegrate into their triangular components, as the true, unchanging, indestructible formal elements of the cosmos, with fire, air, and water being interconvertible. Like Democritus, however, Plato attributes secondary qualities to the sizes, shapes, motions, and interactions of his atoms. However, the later Neoplatonists, the most important being Plotinus (a.d. 205-270), demonstrated virtually no interest in scientific questions.

Apart from Aristotle, the most important rival matter theory to atomism in later Western antiquity was that of the Stoics, named for the stoa or "porch" that was the original site of their school. Originating with Zeno of Citium (336?-265? b.c.), Stoic philosophy was developed by Chryssipus of Soli (280?-206? b.c.) in a systematic fashion that included cosmological doctrines. Later Stoics of importance included the Roman poet Seneca (4? b.c.-a.d. 65) and the Roman emperor Marcus Aurelius (a.d. 121-180), though their interests lay primarily in religion and ethics.

Inspired by Heraclitus and other pre-Socratics, the Stoics held that the cosmos is a single eternal substance, a kind of universal living being animated by a pervasive "spirit" (pneuma) or "soul" (psyche), with fire as a divine, active, material principle of creativity. This primeval fire acted as a creative force on a precosmic moisture to generate the cosmos, with "seeds" (spermata) of the pneuma moisture blend inseminating all things. As a conceptually divisible but actually undivided material plenum, the cosmos is harmoniously unified and strengthened by a universal "tension" (tonos), a property resulting from opposing forces acting in the intangible pneuma as a material medium. The tonos transmits causal "impulses" from one body to another, like the vibrations of a plucked lyre string or the stretching of an athlete's tendons. The entire cosmos is subject to a recurring cycle of conflagration and regeneration, due to an alternating tension between the destructive and creative aspects of the primeval fire.

Stoic matter theory likewise presented a remarkable synthesis of old and new ideas. All real things—even knowledge, virtues, and vices—are material "bodies" (somata) with capacities for acting upon, and being acted upon or resisting action by, other bodies. The original combination of pneuma with moisture differentiated an initially qualityless primal matter into the traditional four basic elements of ordinary fire, air, water, and earth, by a process of rarefaction and condensation. The elements formed four concentric layers, with fire at the perimeter, followed by air and then water, with earth at the center, subsequently undergoing further inter-mixture. Rejecting Aristotle's complex scheme of complementary pairs of primary elemental qualities, the Stoics adopted the simpler association of each element with a single primary quality—fire:hot, air:cold, water:wet, earth:dry—made by a pupil of Empedocles, Philistion of Locri.

Particularly controversial was the Stoic doctrine of "total blending" (synchysis). The pre-Socratics had struggled with the distinction between chemical combination and physical mixture. Because they denied any possibility of material generation out of or destruction into nothingness, they proposed only theories in which initial components were juxtaposed or mixed in ways that preserved them unaltered in the final product. Aristotle's theories of elemental transformation and combination (mixis) allowed for generation and destruction of substances in a restricted but not absolute sense. But the Stoics asserted that because the entire cosmos is a single substance, with all bodies being pervaded by the pneuma as a creative and transforming agent, two different bodies can be completely fused and fully interpenetrate one another to form a single new body. A favorite example was the penetration of heated iron by fire. Critics of the Stoics accused them—wrongly, some scholars think—of believing that two bodies can occupy the same place at the same time, a logical impossibility according to the Greek concept of place as a distinct relational location.

The power of Aristotle's own philosophical system, and his penetrating criticisms of the flaws in those of his rivals, ultimately led to the demise of the atomist and Stoic schools during the third century a.d. The rise of Christianity was another major factor, since the basic theism of Aristotle's system proved far more compatible with Christian theology than the atomists' implicit atheism or Stoic pantheism. Atomism as a scientific theory would only be revived in the seventeenth century, and then in a drastically revised fashion. Stoic physics has received renewed attention from historians and philosophers only in recent decades, for ideas in it that faintly foreshadow concepts of modern quantum physics. Nevertheless, all three systems, and those of their pre-Socratic predecessors, contributed profoundly to the intellectual richness and complexity of theories of matter, energy, and physical and chemical interactions in the Western scientific tradition.

JAMES A. ALTENA