Atomism

Atomism, derived from the Ancient Greek term ἄτομον (atomon), meaning 'uncuttable, indivisible', is a philosophical concept positing that the physical cosmos consists of fundamental, indivisible constituents referred to as atoms.

The philosophical concept of atomism, along with its constituent 'atoms,' emerged independently in both ancient Greek and ancient Indian traditions. In ancient Greece, the earliest documented proponent of atomism is Leucippus, who is generally recognized for originating this theory. Leucippus and other early Greek atomists posited that reality comprises two primary elements: atom and void. They theorized that the diverse macroscopic substances observed in the world result from the aggregation of atoms in various shapes, arrangements, and spatial configurations.

A parallel concept was advanced by Kanāda of the Vaiśeṣika school, who introduced the notion of indivisible particles, termed paramāṇu. Furthermore, Indian Buddhist thinkers, including Dharmakirti (fl. c. 6th or 7th century), formulated unique atomistic theories, notably incorporating the idea of momentary or instantaneous atoms (kalapas) that transiently appear and disappear.

During the early 19th century, chemists and natural philosophers experimentally identified particles of chemical matter, which they initially considered indivisible. John Dalton subsequently designated these particles 'atoms,' a term previously established within atomist philosophy. While the link to ancient atomism remains largely indirect, contemporary elementary particles serve as a modern conceptual parallel to the philosophical atoms of antiquity.

Reductionism

Philosophical atomism presents a reductionist argument, asserting that while all phenomena are constituted by atoms and void, the composite entities themselves lack true existence. Instead, it posits that the sole realities are atoms mechanically interacting within an otherwise empty void. The Greek philosopher Democritus was a notable advocate of this theory.

Conventionally, sweetness is sweet, bitterness is bitter, heat is hot, cold is cold, and color is color. However, in actuality, only atoms and the void exist.

Atomism contrasts sharply with substance theories, which propose that a fundamental material continuum retains its qualitative properties even when divided (e.g., the proportions of the four classical elements would remain constant in any segment of a homogeneous substance).

Antiquity

Greek Atomism

Democritus

During the 5th century BC, Leucippus and his student Democritus advanced the theory that all matter consists of minute, indivisible particles, which they termed 'atoms.' While virtually no information about Leucippus exists beyond his role as Democritus's instructor, Democritus himself was a prolific author, reportedly composing over eighty treatises. Although none of these works have survived intact, a substantial collection of fragments and quotations from his writings persists, serving as the primary source for understanding his atomic doctrines. Democritus's rationale for the existence of atoms rested on the premise that infinite division of matter is impossible, thereby necessitating its composition from extremely small particles. This atomistic theory sought to reconcile the "distinction which the Eleatic school drew between the Absolute, or the only real existence, and the world of change around us."

Democritus posited that atoms are imperceptible to human senses, infinite in number and variety, and eternal. These atoms, he asserted, traverse a vacuum, which he designated the 'void,' exhibiting variations in shape, arrangement, and orientation. He described some atoms as convex, others concave, and some resembling hooks or eyes. They are in perpetual motion, constantly engaging in collisions. Democritus contended that only atoms and the void possess true existence, with all other phenomena being merely conventional constructs. The objects encountered in daily life are formed from numerous atoms coalescing through random impacts, their shapes and material properties determined by their atomic composition. Similarly, human sensory experiences are also attributed to atomic interactions. For instance, bitterness results from small, angular, jagged atoms stimulating the tongue, while sweetness arises from larger, smoother, more rounded atoms interacting with it.

Parmenides previously asserted the non-existence of motion, change, and void. He posited that all existence constituted a singular, all-encompassing, and immutable mass, a philosophical stance known as monism, viewing change and motion as mere illusions. He explicitly dismissed sensory experience as a means to comprehend the universe, advocating instead for purely abstract reasoning. Parmenides equated the void with non-being, thereby concluding that motion was impossible due to the absence of any space into which movement could occur. He contended that what is not does not exist, implying the non-existence of the void rather than explicitly denying it. Furthermore, he argued that all that is must form an indivisible unity, as multiplicity would necessitate a void for division. Ultimately, he declared this all-encompassing Unity to be immutable, having already encompassed all potential and actual existence.

Democritus, in contrast, rejected Parmenides' assertion that change was illusory, arguing for its reality or, at minimum, the necessity of explaining such an illusion. Consequently, he endorsed the concept of the void, proposing that the universe comprises numerous Parmenidean-like entities that traverse this void. The void, being infinite, furnishes the space enabling atoms to arrange themselves in diverse configurations, either packing densely or scattering. These varied atomic packings and scatterings within the void constitute the dynamic forms and masses of objects perceived by organisms through touch, sight, ingestion, hearing, smell, and taste. Although organisms experience sensations like hot or cold, these qualities lack intrinsic existence, being merely subjective perceptions generated by the distinct atomic arrangements within the void that compose the object being sensed as "hot" or "cold."

Democritus's original works are extant solely through secondhand accounts, some of which are considered unreliable or contradictory. A significant portion of the most compelling evidence for Democritus's theory of atomism derives from Aristotle (384–322 BCE), particularly in his analyses comparing Democritus's and Plato's divergent perspectives on the fundamental indivisible components of the natural world.

Unit-point atomism

Certain twentieth-century philosophers posited that unit-point atomism represented the philosophical doctrine of the Pythagoreans, conceived as a deliberate rejection of Parmenides and the Eleatics. This theory asserted that atoms, though infinitesimally small ("point-like"), nonetheless possessed corporeality, thereby serving as a precursor to Democritean atomism. However, the majority of contemporary scholars of Presocratic philosophy, including Kurt von Fritz, Walter Burkert, Gregory Vlastos, Jonathan Barnes, and Daniel W. Graham, have refuted the applicability of any form of atomism to the early Pythagoreans (prior to Ecphantus of Syracuse).

The concept of unit-point atomism was introduced to interpret a statement attributed to Zeno of Elea within Plato's Parmenides: "these writings of mine were meant to protect the arguments of Parmenides against those who make fun of him. . . My answer is addressed to the partisans of the many. . ." It was hypothesized that the anti-Parmenidean pluralists were unit-point atomists whose philosophical tenets fundamentally opposed the Eleatics. Nevertheless, this hypothesis, proposed to elucidate Zeno's paradoxes, has since been comprehensively discredited.

Geometry and atoms

Plato (c. 427 – c. 347 BCE) contended that the mere collision of atoms could not account for the inherent beauty and structured form observed in the world. In his dialogue Timaeus (28b–29a), the character Timaeus asserted that the cosmos was not eternal but rather a creation, fashioned by its creator according to an everlasting and immutable paradigm.

A constituent element of this creation comprised the four fundamental bodies: fire, air, water, and earth. However, Plato did not regard these corpuscles as the ultimate level of reality; instead, he believed they were composed of a more fundamental, unchanging mathematical reality. These elementary bodies manifested as geometric solids, whose faces, in turn, were constructed from triangles. Specifically, the square faces of the cube were each formed by four isosceles right-angled triangles, while the triangular faces of the tetrahedron, octahedron, and icosahedron were each composed of six right-angled triangles.

Plato theorized the geometric configurations of the fundamental bodies comprising the four elements, as presented in the accompanying table. The stable, flat-based cube was associated with earth. Fire was linked to the tetrahedron due to its sharp, penetrating points and edges, which conferred mobility. Conversely, the blunter points and edges of the octahedron and icosahedron rendered them less mobile, leading to their assignment to air and water, respectively. Plato's model provided a credible explanation for transformations among primary substances, positing that these simple bodies could be disassembled into triangles and subsequently reconfigured into atoms of distinct elements.

Aristotelian Rejection of Atomism

Prior to 330 BCE, Aristotle posited that the elements—fire, air, earth, and water—were continuous rather than composed of discrete atoms. He contended that the void, a prerequisite for atomic theories, contravened fundamental physical principles. Aristotle's philosophy asserted that change occurred through the transformation of matter from its potential state to a new actuality, rather than via the rearrangement of atoms into novel structures. For instance, a potter's manipulation of wet clay actualizes its potential to become a drinking mug. While Aristotle frequently faces criticism for his rejection of atomism, it is noteworthy that in ancient Greece, Democritus's atomic theories were considered "pure speculations, incapable of being put to any experimental test."

Aristotle proposed the concept of minima naturalia, defining them as the smallest constituents into which a homogeneous natural substance—such as flesh, bone, or wood—could be divided while preserving its intrinsic character. In contrast to Democritus's atomism, these Aristotelian "natural minima" were not conceived as physically indivisible entities. Instead, Aristotle's framework was grounded in his hylomorphic worldview, which posited that every physical entity comprises both matter (Greek hyle) and an immaterial substantial form (Greek morphe) that confers its essential nature and structure. An illustrative analogy involves a rubber ball: the rubber can be considered the matter enabling the ball to assume various forms, while its spherical shape represents the form that defines its identity as a "ball." However, it is crucial to recognize that even rubber itself would be regarded as a composite of form and matter, possessing a degree of identity and determinacy. Pure or primary matter, conversely, is entirely unformed, unintelligible, and possesses infinite potential for transformation.

Aristotle hypothesized the existence of a minimal size beyond which matter could no longer maintain the structure of substances like flesh, bone, wood, or other organic materials that he considered homogeneous (predating the microscope's invention). For example, if flesh were subdivided past its natural minimum, the remnants might consist primarily of water, along with smaller quantities of other elements. Crucially, any remaining water or other elements would no longer possess the inherent "nature" of flesh. In hylomorphic terminology, they would cease to be matter structured by the form of flesh; instead, the residual water, for instance, would be matter structured by the form of water, distinct from the form of flesh.

Epicurus's Contributions

Epicurus (341–270 BCE) pursued studies in atomism under Nausiphanes, a former pupil of Democritus. While Epicurus firmly believed in the existence of atoms and the void, he expressed reservations about humanity's capacity to fully elucidate specific natural phenomena, including earthquakes, lightning, comets, or lunar phases. The limited surviving works of Epicurus primarily demonstrate his dedication to applying Democritus's theories to empower individuals to assume responsibility for their own well-being and happiness, based on his conviction that no deities would intervene to assist them. (Epicurus conceptualized gods as embodying moral exemplars.)

Indian Atomistic Philosophy

Early manifestations of atomistic thought are evident in the writings of the Vedic sage Aruni, who lived in the 8th century BCE. Notably, Aruni proposed that "particles too small to be seen mass together into the substances and objects of experience," a concept referred to as kaṇa. It is important to distinguish that kana denotes "particles" rather than atoms (paramanu). Scholars such as Hermann Jacobi and Randall Collins have drawn parallels between Aruni and Thales of Miletus, citing their shared scientific methodology and labeling them "primitive physicists" or "proto-materialist thinkers." Subsequently, the Charvaka and Ajivika schools of atomism emerged as early as the 7th century BCE. Bhattacharya suggests that Charvaka might have been one of several atheistic, materialist philosophical traditions present in ancient India.

Kaṇāda, recognized as the founder of the Vaiśeṣika school within Indian philosophy, characterized atoms (paramāṇu) as eternal, indivisible, and imperceptible entities that coalesce to form all material substances. He posited that reality comprises nine fundamental constituents: four categories of atoms (earth, water, light, and air), space (akasha), time (kāla), direction (disha), an infinite number of souls (Ātman), and mind (manas). Kaṇāda's atomic theory was likely developed independently of similar concepts in ancient Greece, given the theoretical distinctions. For instance, Kaṇāda proposed that atoms, as fundamental building blocks, possess both qualitative and quantitative differences, whereas Greek atomists generally suggested only quantitative variations.

The Nyaya–Vaisesika school formulated theories concerning the aggregation of kaṇas into more intricate structures; scholarly dating places the Nyaya and Vaisesika texts between the 9th and 4th centuries BCE. Vaisesika atomists posited four elemental atom types, yet Vaisesika physics attributed 25 distinct possible qualities to atoms, categorized into general extensive properties and specific intensive properties. The Nyaya–Vaisesika atomists developed elaborate models for atomic combination. Within Vaisesika atomism, atoms initially combine to form Dvyaṇuka (dyads) and tryaṇukas (triads) before further aggregating into perceptible bodies.

Certain doctrines within these atomistic traditions exhibit "suggestive similarities" to those articulated by Democritus. McEvilley (2002) hypothesizes that such resemblances stem from extensive cultural interaction and diffusion, likely occurring in both directions.

Late Roman Republic

Lucretius's Revival of Epicureanism

The philosophical tenets of Epicurus were reasserted in the writings of his Roman adherent, Lucretius (c. 99 BC – c. 55 BC), particularly in his seminal work, On the Nature of Things. This Classical Latin scientific treatise, presented in poetic form, elucidates various aspects of Epicurean theory regarding the universe's evolution to its current state. It demonstrates that perceived phenomena are, in fact, composite formations. Atoms and the void are depicted as eternal and in perpetual motion. Atomic collisions are posited as the mechanism for object creation, with these objects remaining composed of the same eternal atoms whose motion is temporarily integrated into the newly formed entity. Lucretius further explains human sensations and meteorological phenomena through the lens of atomic motion.

Atoms and the Void Versus Religion

In his epic poem On the Nature of Things, Lucretius portrays Epicurus as a heroic figure who vanquished the "monster Religion" by enlightening humanity about the atomic possibilities and impossibilities. However, Epicurus himself advocated a non-aggressive stance, encapsulated by his declaration:

The man who best knows how to meet external threats makes into one family all the creatures he can; and those he can not, he at any rate does not treat as aliens; and where he finds even this impossible, he avoids all dealings, and, so far as is advantageous, excludes them from his life.

Nevertheless, according to the science historian Charles Coulston Gillispie:

The atomic doctrine, as integrated into Epicurean philosophy, was inherently incompatible with established moral authority.

Epicurean deities neither participated in the creation of the world nor exercised any oversight. Lucretius asserted that "Nature is free and uncontrolled by proud masters and runs the universe by herself without the aid of gods." Among Greek scientific perspectives, atomism was uniquely irreconcilable with theological frameworks. Epicurus and Lucretius championed atomism as a means of intellectual liberation, aiming to dismantle religious claims and emancipate individuals from superstition and the ignoble dread of arbitrary gods. Consequently, any suggestion of Epicurean thought became anathema in Christian Europe, leading to its profound misrepresentation, perhaps more so than any other philosopher except Machiavelli.

The acceptance or rejection of a vacuum's possibility was intrinsically linked to the theories of atoms and atomism, as the vacuum constituted an integral component of this philosophical framework.

Democritus and Lucretius posited the necessity of a vacuum existing between the discrete particles (atoms) that they believed constituted all matter, thereby refuting the impossibility of a vacuum. Nevertheless, the prevailing view until the close of the sixteenth century was the near-universal conviction that a vacuum was impossible. Although the intellectual climate was conducive to a resurgence of belief in the vacuum's possibility, the concept itself remained anathema to religious authorities, primarily due to its association with the atomistic theories of Epicurus and Lucretius, which were deemed heretical.

Roman Empire

Galen

Although Aristotelian philosophy largely overshadowed the significance of atomistic thought during the late Roman and medieval European periods, the works of the atomists were nonetheless preserved and elucidated within commentaries on Aristotle's writings. Notably, in the 2nd century, Galen (129–216 CE) provided comprehensive analyses of the Greek atomists, with a particular focus on Epicurus, within his own Aristotelian commentaries.

Middle Ages

Medieval Hinduism

The Ajivika, a "Nastika" philosophical school, incorporated a theory of atoms or atomism into its metaphysics, which was subsequently integrated into the Vaiśeṣika school. The Vaiśeṣika school posited that all physical objects in the universe are ultimately reducible to paramāṇu (atoms), and individual experiences arise from the complex interplay of substance (determined by atoms, their quantity, and spatial configurations), quality, activity, commonality, particularity, and inherence. This framework asserted that all phenomena were atom-composed, with qualities emerging from atomic aggregates, yet the formation and characteristics of these atoms were preordained by cosmic forces. The traditional name of the school's founder, Kanada, translates to 'atom eater,' and he is recognized for establishing the foundational principles of an atomistic approach to physics and philosophy within the Sanskrit text Vaiśeṣika Sūtra, also known as Kanada Sutras or Aphorisms of Kanada.

Medieval Buddhism

Medieval Buddhist atomism, which gained prominence around the 7th century, diverged considerably from the atomistic doctrines articulated in earlier Buddhist thought. Philosophers such as Dharmakirti and Dignāga conceptualized atoms as dimensionless points, devoid of duration, and composed of energy. Fyodor Shcherbatskoy (1930), in his comparative analysis of these two systems, emphasized their shared principle: the postulation of "absolute qualities" (guna-dharma) as the fundamental substratum of all empirical phenomena.

Subsequently, the Abhidhammattha-sangaha, a text originating from the 11th or 12th century, posits the existence of rupa-kalapa. These are conceptualized as the most diminutive units of the physical world, characterized by diverse elementary compositions. Although imperceptible under ordinary conditions, the rupa-kalapa are reportedly rendered visible through the practice of meditative samadhi.

Medieval Islam

Atomistic philosophies emerged very early within Islamic thought, drawing initial influence from earlier Greek and, to a lesser extent, Indian philosophical traditions. Islamic speculative theology frequently addressed questions in physics through an atomistic conceptual framework.

Mu'tazilite Atomism

Mu'tazilite atomism, an early Islamic theological cosmological concept, posits that the universe comprises discrete, indivisible parts (juz’ lā yatajazzā) created by God. This foundational idea also underpins the Mu'tazila's rejection of determinism. By asserting an atomized nature, this school of thought considers humans capable of independent action (mubasharah), thereby meriting rewards or punishments commensurate with their deeds. This aligns with the principle that moral good and evil are rational and intrinsic to an action's essence, rather than solely a consequence of divine decree. Prominent Mu'tazilite theologians and philosophers associated with atomistic concepts include Abu al-Hudhayl Al-'Allaf and Al-Jubba'i, although some, like Ibrahim al-Nazzam, expressed skepticism towards atomism.

Al-Ghazali and Ash'arite Atomism

The Ash'arite school of Islamic theology developed the most influential form of Islamic atomism, prominently articulated in the works of the theologian al-Ghazali (1058–1111). Within Ash'arite atomism, atoms constitute the sole perpetual material entities, while all other phenomena are deemed "accidental," existing only momentarily. No accidental entity can serve as a cause for another, with the exception of perception, which itself is momentary. Contingent events are not governed by natural physical causes but arise directly from God's continuous intervention, without which no occurrence would be possible. Consequently, nature is entirely contingent upon God, a concept consistent with other Ash'arite Islamic perspectives on causation, or its absence. Al-Ghazali further employed this theory to bolster his doctrine of occasionalism. Notably, Ash'arite atomism exhibits greater conceptual affinity with Indian atomism than with its Greek counterpart.

Averroes' Rejection of Atomism

Conversely, other Islamic intellectual traditions repudiated Ash'arite atomism, instead elaborating upon numerous Greek texts, particularly those by Aristotle. A prominent philosophical school in Al-Andalus, featuring the renowned commentator Averroes (1126–1198 CE), explicitly disavowed al-Ghazali's ideas and engaged in a comprehensive analysis of Aristotelian philosophy. Averroes produced detailed commentaries on the majority of Aristotle's works, which subsequently exerted significant influence on Jewish and Christian scholastic thought.

Medieval Christendom

According to Joshua Gregory, a historian of atomism, no substantial advancements in atomistic theory occurred between Galen's era and its revival in the 17th century by Isaac Beeckman, Gassendi, and Descartes. Gregory characterizes this intervening period as "the exile of the atom," asserting that "it is universally admitted that the Middle Ages had abandoned Atomism, and virtually lost it."

Scholasticism

Despite the unavailability of ancient atomistic texts, scholastic thinkers progressively encountered Aristotle's critiques of atomism through the Latin translations of Averroes's commentaries. While Epicurean atomism had waned in prominence during the Scholastic centuries, the Aristotelian concept of minima naturalia garnered considerable attention. Philosophical discourse surrounding minima naturalia furnished a conceptual foundation for the mechanistic philosophy of early modern figures like Descartes, as well as for the alchemical treatises of Geber and Daniel Sennert, who subsequently influenced the corpuscularian alchemist Robert Boyle, a pivotal figure in the establishment of modern chemistry.

A central concern in late Roman and Scholastic interpretations of this concept involved harmonizing minima naturalia with the overarching Aristotelian principle of infinite divisibility. Commentators such as John Philoponus and Thomas Aquinas resolved these facets of Aristotle's philosophy by differentiating between mathematical and "natural" divisibility. Throughout much of the Middle Ages, the curriculum in European universities largely adhered to such Aristotelian frameworks, with only minor deviations.

Nicholas of Autrecourt

Nevertheless, atomistic ideas did emerge within medieval universities. For instance, in the 14th century, Nicholas of Autrecourt posited that matter, space, and time were composed of indivisible atoms, points, and instants, respectively, and that all processes of generation and corruption resulted from the rearrangement of material atoms. The conceptual parallels between his theories and those of al-Ghazali imply that Nicholas might have encountered Ghazali's work, possibly via Averroes's refutation of it.

Atomistic Renaissance

17th Century

The 17th century witnessed a resurgence of interest in Epicurean atomism and corpuscularianism, which emerged either as a hybrid model or a distinct alternative to Aristotelian physics. Prominent figures instrumental in this revival of atomism included Isaac Beeckman, René Descartes, Pierre Gassendi, and Robert Boyle, alongside other significant contributors.

The Northumberland Circle

Among the earliest proponents of atomism in England was the Northumberland Circle, a collective of amateur scientists led by Henry Percy, 9th Earl of Northumberland (1564–1632). Despite their limited publications, this group played a crucial role in disseminating atomistic concepts within England's developing scientific community. Their influence may have extended particularly to Francis Bacon, who adopted atomism around 1605 before subsequently rejecting certain aspects of the theory. Although they revitalized classical atomism, the Northumberland Circle represented a scientific avant-garde, encompassing nearly half of the documented Copernicans before 1610, the year Galileo published The Starry Messenger. Other notable atomists from the late 16th and early 17th centuries included Giordano Bruno, Thomas Hobbes (who also modified his views on atomism later in his career), and Thomas Hariot. Concurrently, diverse atomistic theories were also flourishing in France.

Galileo Galilei

Galileo Galilei (1564–1642) championed atomism in his 1612 work, Discourse on Floating Bodies (Redondi 1969). Later, in The Assayer, Galileo presented a more comprehensive physical framework grounded in a corpuscular theory of matter, positing that all phenomena, except sound, result from "matter in motion."

Perceived Versus Real Properties

Leading proponents of atomism linked the theory to the concept that certain apparent properties of objects are subjective constructs of the perceiving mind, categorizing them as "secondary" qualities distinct from "primary" qualities. Through his experimental investigations, Galileo identified fundamental issues within Aristotelian physics. He partially adopted atomism as an alternative framework, though he never fully committed to it. For instance, his experiments involving falling bodies and inclined planes led to his formulations of circular inertial motion and accelerating free-fall. The prevailing Aristotelian theories of impetus and terrestrial motion proved insufficient to account for these observations. While atomism itself did not fully elucidate the law of fall, it offered a more promising conceptual foundation for developing such an explanation, primarily because ancient atomism, unlike Aristotelian physics, posited the conservation of motion.

René Descartes

René Descartes' (1596–1650) "mechanical" philosophy of corpuscularism shared significant commonalities with atomism, and is sometimes regarded as a variant thereof. Descartes posited that all physical entities in the universe were composed of minute vortices of matter. Similar to ancient atomists, Descartes asserted that sensations, such as taste or temperature, resulted from the shape and size of these minute material particles. In his 1644 work, Principles of Philosophy, he stated: "The nature of body consists just in extension—not in weight, hardness, colour or the like." A primary divergence between atomism and Descartes' framework concerned the existence of a void. Descartes contended that a vacuum was impossible, with all matter perpetually swirling to preclude any void as corpuscles traversed through other matter. A further crucial distinction between Descartes' perspective and classical atomism was his mind-body duality, which established an independent domain of existence for thought, the soul, and, critically, God.

Pierre Gassendi

Pierre Gassendi (1592–1655), a French Catholic priest, was also a dedicated natural philosopher. Gassendi's atomic theory more closely resembled classical atomism, notably devoid of atheistic implications. Deeply fascinated by the Greek atomists, he endeavored to "purify" atomism by divesting it of its perceived heretical and atheistic philosophical tenets (Dijksterhius 1969). Gassendi's formulation of a mechanical philosophy based on atomism was partly a reaction to Descartes, specifically opposing Descartes' reductionist assertion that only purely mechanical explanations in physics were valid, and his comprehensive application of geometry to physical phenomena.

Johann Chrysostom Magnenus

Johann Chrysostom Magnenus (c. 1590 – c. 1679) published his work Democritus reviviscens in 1646. He was the first to provide a scientific estimation of the size of an "atom," a term that would now correspond to a molecule. Through an experiment involving the combustion of incense until its scent permeated a large church, Magnenus determined the number of molecules within a single grain of incense to be approximately 10¹⁸, a calculation remarkably close to the actual value, differing by only one order of magnitude.

Atomism and Corpuscularianism

Corpuscularianism shares similarities with atomism, yet it posits that corpuscles, unlike the indivisible atoms, are theoretically divisible. This distinction allowed for theories such as mercury's ability to permeate and alter the internal structure of metals, a concept relevant to the alchemical pursuit of gold transmutation. Prominent advocates of corpuscularianism linked it to the notion that certain perceived properties of objects are subjective constructs of the mind, categorizing them as 'secondary' qualities distinct from 'primary' qualities. However, not all forms of corpuscularianism incorporated this primary-secondary quality differentiation. An influential school of thought in medieval and early modern alchemy contended that chemical analysis demonstrated the persistence of stable corpuscles, which maintained their integrity within chemical compounds (in modern terminology). William R. Newman has termed this specific material theory "chymical atomism," emphasizing its importance to both mechanical philosophy and the chemical atomism that developed in the early 19th century.

Corpuscularianism remained a prevalent theory for several centuries, maintaining its connection to alchemy through the contributions of 17th-century scientists like Robert Boyle (1627–1692) and Isaac Newton. Newton, for example, applied this concept in formulating his corpuscular theory of light. The version adopted by most English scientists following Robert Boyle's work represented a synthesis of the theories proposed by Descartes and Gassendi. In his 1661 treatise, The Sceptical Chymist, Boyle highlighted challenges within chemistry and proposed atomism as a potential explanatory framework. The overarching principle that ultimately facilitated the adoption of a combined corpuscular-atomistic view was mechanical philosophy, which gained widespread acceptance across the physical sciences. Boyle typically designated indivisible particles as minima naturalia or prima naturalia, seldom employing the term "atom."

Mikhail Lomonosov

In his 1744 publication, Meditations on the Cause of Heat and Cold, the Russian polymath Mikhail Lomonosov precisely characterized corpuscles as composite particles, stating: "An element is part of a body which is not composed of any other smaller body ... A corpuscle is a collection of elements which constitute one small mass." Subsequently, in a 1748 study, he substituted "atom" for "element" and "particula" (particle) or "molecule" for "corpuscle."

Modern Atomic Theory

Late 18th Century

Towards the close of the 18th century, the practical advancements in engineering and technology started to inform philosophical interpretations concerning the fundamental composition of matter. Consequently, theorists exploring the ultimate nature of matter increasingly sought to corroborate their conceptual "thought experiments" with reproducible empirical demonstrations whenever feasible.

Roger Boscovich (1711–1787), a polymath from Ragusa, formulated the inaugural comprehensive mathematical theory of atomism. This theory drew upon the concepts of Newton and Leibniz, yet Boscovich reconfigured them to establish a foundational framework for atomic physics.

19th Century

John Dalton

In 1808, the English physicist John Dalton (1766–1844) synthesized extensive existing experimental data to articulate the empirical evidence regarding the composition of matter. He observed that distilled water consistently yielded the same constituent elements, hydrogen and oxygen, regardless of its origin. Likewise, other purified compounds invariably decomposed into identical elements in fixed proportions by weight.

Consequently, it can be inferred that the fundamental particles comprising all homogeneous substances exhibit identical characteristics in terms of weight, form, and other properties. This implies that each particle of water is indistinguishable from any other water particle, and similarly for hydrogen particles, among others.

Dalton further asserted the existence of a distinct atom for every element, aligning with Lavoisier's definition of an element as an indivisible substance. Consequently, Dalton presented the following conclusions:

He posited that chemical analysis and synthesis are limited to the separation and recombination of existing particles. Dalton argued that chemical processes cannot create or destroy matter, stating that attempting to do so would be as futile as introducing a new planet into the solar system or annihilating an existing one. He maintained that all observable chemical transformations involve merely the dissociation of cohesive or combined particles and the subsequent joining of previously separate ones.

Subsequently, Dalton provided a compilation of relative weights for the constituent elements in various common compounds, summarizing his findings as follows:

First, he proposed that water is a binary compound composed of hydrogen and oxygen, with the approximate relative weights of their elementary atoms being 1:7;

Second, he stated that ammonia is a binary compound of hydrogen and nitrogen, with the approximate relative weights of these two atoms being 1:5.

Dalton inferred that the consistent elemental proportions by weight indicated that atoms of one element combine with a restricted number of atoms from other elements to constitute the compounds he enumerated.

Atomic Theory Controversy

Dalton's atomic theory faced considerable controversy throughout the 19th century. While the Law of Definite Proportions gained acceptance, the underlying atomic hypothesis was not universally embraced. For instance, in 1826, upon presenting Dalton with the Royal Medal from the Royal Society, Sir Humphry Davy remarked that the theory's utility emerged only when its atomic premise was disregarded. In 1866, English chemist Sir Benjamin Collins Brodie published the initial segment of his *Calculus of Chemical Operations*, proposing a non-atomic alternative to the atomic theory, which he characterized as a 'Thoroughly materialistic bit of joiners work'. Conversely, in 1869, English chemist Alexander Williamson utilized his Presidential Address to the London Chemical Society to advocate for atomic theory against its detractors. This defense prompted subsequent gatherings where positivists reiterated their objections to the existence of atoms. The debate ultimately concluded in Dalton's favor during the early 20th century, coinciding with the emergence of atomic physics.

The 20th Century

Experimental Verification

Although atoms and molecules had long been hypothesized as the fundamental components of matter, definitive evidence remained elusive. In 1905, Albert Einstein published a seminal paper explaining that the motion observed by Scottish botanist Robert Brown was caused by individual water molecules impacting pollen particles, marking one of Einstein's early scientific contributions. This elucidation of Brownian motion provided compelling evidence for the existence of atoms and molecules, a concept further substantiated experimentally by French physicist Jean Perrin (1870–1942) in 1908. Perrin later received the Nobel Prize in Physics in 1926 for his groundbreaking work on the discontinuous structure of matter. The erratic nature of Brownian motion arises from the constantly shifting direction of atomic bombardment, causing particles to be struck unevenly from various sides.

Eliminative Materialism

• Eliminative materialism
• First Principle
• History of Chemistry
• Mereological Nihilism
• Montonen–Olive Duality: Philosophical Implications
• Ontological Pluralism
• Physicalism
• Prima Materia
• Process Philosophy

References

Citations

References

Dictionary of the History of Ideas: Atomism from Antiquity to the Seventeenth Century

• Dictionary of the History of Ideas: Atomism: Antiquity to the Seventeenth Century
• Dictionary of the History of Ideas: Atomism in the Seventeenth Century
• Jonathan Schaffer, "Is There a Fundamental Level?" Nous 37 (2003): 498–517. (Authored by a philosopher critical of atomism)
• An article discussing traditional Greek atomism
• Atomism from the 17th to the 20th Century, available at the Stanford Encyclopedia of Philosophy