Natural philosophers in Greece developed two rival cosmological systems: Atomism and Aristotelianism. Describe the origins and characteristics of both systems, including their ontological and epistemological characteristics. What questions were these systems intended to solve?
The cosmos, at first glance, is awe inspiring. It seems to go on endlessly in every direction and each heavenly body seems to glimmer in eternity. Questions of the nature of the heavens lie at the core of humanity, and the Ancient Greeks developed many different interpretations of how the universe was designed and constructed. Atomism and Aristotelianism were two such theories that sought to fathom the wonders of the cosmos. The former was developed in a joint effort by Leucippus and Democritus, and the latter by the eminent Aristotle and his followers. Each of these two systems uniquely addressed various ontological and epistemological issues. Although Atomism and Aristotelianism offer similar cosmological systems, their approaches, claims, and methods are indeed very different.
Atomism was first proposed by the Pre-Socratic philosophers Leucippus and Democritus. The Atomic theory states that the cosmos contain two things: nothingness, or the void, and the indivisible buliding blocks of all matter called atoms (from the Greek atomos, meaning indivisible). According to the atomists, the atom is the fundamental "stuff" of the universe, while the void is the space between particles. Lucretius, a Roman Epicurean, justified the idea of the void in his scientific poem De Rerum Natura, or On the Nature of Things. He wrote, "things are not hemmed in by the pressure of solid bodies in a tight mass. This is because there is vacuity in things....Well then, by vacuity I mean intangible and empty space. If it did not exist, things could not move at all" (Lucretius 16). These mobile particles can come in various shapes, but because of their diminutive size, they escape the naked eye. The original atomists said that atoms had only size and shape, but our perception of secondary properties such as color and texture are associated with the arrangement of the atoms in an object. Their shapes are extremely varied. Aristotle said in his work On Democritus that " [Democritus] thinks that the substances are so small that they escape our senses, and that they possess all sorts of forms and all sorts of shapes and differences in magnitude... for some of them are uneven, some hooked, some concave, some convex, and others have innumberable other differences" (Barnes 247). The atoms appear to follow straight lines from collision to collision, interacting to make up the things that we see. These secondary properties that are perceived by humans through our senses (e.g. color, texture, taste, etc.) aren't really innate properties, according to Democritus, but are merely sensations created by the different arrangements of the atoms. Our perception of change, then, is just an illusion, in concordance with Parmenides' theory.
An important aspect of early atomism is its very mechanical nature. In the early 5th century BCE, Greek natural philosophy began to change. No longer were explanations firmly rooted in divine intervention. Philosophers like Democritus and Leucippus began to base their thinking on order, regularity, and physis or nature. In the minds of atomists, everything that occurs is the necessary outcome of atoms moving according to their nature. Reality is nothing more than the innate motions of these indivisible atoms. This view does not depend on any outside forces, divine or otherwise. As Lucretius remarked, "Certainly the atoms did not post themselves purposefully in due order by an act of intelligence, nor did they stipulate what movements each should perform...they have experienced every variety of movement and conjunction till they have fallen into the particular pattern by which this world of ours is constituted" (Lucretius 17). The lack of a cosmic plan or purpose is what distinguishes Atomism from earlier ideas in cosmology and natural philosophy. Indeed, David Lindberg said that the atomists viewed "reality as a lifeless piece of machinery...Life itself is reduced to the motions of inert corpuscles. No room exists for purpose or freedom; iron necessity rules" (Lindberg 30). This strongly worded evaluation emphasizes the idea that atomism is not only a scientific theory, but a philosophical one as well.
The less appealing aspects of atomism, namely the lack of both a deity and any real purpose for mankind, were later addressed by fellow thinkers. Plato was one such philosopher, who detailed his ontology in a work entitled Timaeus. His view of the universe, unlike his predecessor Democritus's view, possessed a benevolent deity called the Demiurge. By incorporating a deity responsible for cause and purpose, the main features that dismayed certain followers were considerably allayed. Plato's own modified version of atomism is also worthy to note. His geometrical viewpoint cast both equilateral and right triangles as the most fundamental pieces. These pieces combine in a variety of ways to form the Platonic solids (the cube, dodecahedron, tetrahedron, icosahedron, and octahedron) of which four form Empedoclean elements, and one formed the divine element aether. The less rigid shapes took on the elements that Plato thought were more fluid such as water and air. For example the shape that made up water contains 120 triangles making the edges rounder, whereas the shape for earth is a cube and contains only 24 triangles making the edges sharper then those in the shape for water. Also along these lines, the vehicle for change is different combinations of atomic triangles according to Plato.
The aptly named followers of Epicurus, the Epicureans, also endeavored to address the lack of purpose in the initial developments of atomism. Their vehicle of change relied upon a concept known as the "swerve." This "swerve" refers to an uncaused deviation in the otherwise straight downward movement of atoms. As Lucretius, one of the main sources of Epicurean thought, eloquently explains, "When the atoms are traveling straight down through empty space by their own weight, at quite indeterminate times and places they swerve ever so little from their course, just so much that you can call it a change of direction. If not for this swerve, everything would fall downwards like rain-drops through the abyss of space" (Lucretius 16). Such an explanation introduced the concept of free will in the otherwise mechanically deterministic system. The lack of apparent reason for this swerve, though it would seem a philosophical pitfall, allowed humans to break free of destiny's chains. The issue of chance is also brought into play, leading to the concept of multiple worlds. According to atomists, the amount of atoms is infinite, and by extension, so is the universe. Due to both this belief and the introduction of chance, courtesy of the "swerve" in atoms, the atomists believed that the existence of other worlds was certainly possible. Indeed, "this follows from the fact that our world has been made by nature through the spontaneous and casual collision and the multifarious, accidental, random and purposeless congregation and coalescence of atoms whose suddenly formed combinations could serve on each occasion as the starting-point of substantial fabrics" (Lucretius 17). Armed with merely the basic properties assigned to atoms, the atomists developed their cosmology.
Aristotle, however, was not a supporter of atomism, as it did not coincide with his personal cosmological system. Aristotelianism, as the name would imply, is the school of thought founded by Aristotle and continued by his followers. Aristotle was a Greek philosopher and noted biologist who studied under Plato, another Greek philosopher, whose repertoire of pupils included Alexander the Great. Aristotelianism covers a wide array of subjects such as cosmology (the study of the origin and the general structure of the universe), teleology (the study of evidence of purposes in the natural world), ontology (the study of the nature of being), and epistemology (the study of the nature, methods, and limits of human knowledge), and logic (he studied the kinds of arguments that one can make). Aristotle's famous syllogistic argument was an excellent example of his work in logic. An example of a syllogistc argument is: "If all men are mortal and Socrates is a man, then we know that Socrates is mortal." Aristotle was a multidisciplinary man whose focus on biology greatly impacted his natural philosophy and created a new discipline for scholars to investigate. While we only have bits and pieces of his works that are formed like lecture notes, we know that his ideas not only eclipsed previous work from the Pre-Socratics, but also were used and studied by scholars for nearly 2,000 years. Aristotle's works also indicate that he was both a staunch materialist and empiricist. For this Greek, nothing existed beyond what can be directly experienced in the material world, and one must practice careful observation on the nature of things in order to arrive at the truth.
Through such meticulous observation and study, Aristotle understood the need to answer the centuries-old question of the Pre-Socratics: how does one account for change? While atoms moved like rain falling from the heavens, occasionally swerving, combining, separating, and re-combining, Aristotle, as Lindberg explains, "went on to argue that change in form takes place between a pair of opposites, or contraries, one of which is the form to be achieved, the other its privation or absence" (Lindberg 49). These opposites were the dichotomies between dry/wet and hot/cold. By adding or removing heat and moisture, matter was able to take on new forms. He adopted the notion of elements, fire, water, air, and earth to be representations of combinations of temperature and wetness. Moreover, contrary to Parmenides claim that beings are only divided into things that do exist and things that do not, Aristotle added in the concept of "potential being." The potential being and the "actual being" justify change without violating the decree that something cannot come from nothing.
To further clarify his theories of change, Aristotle emphasized knowledge of causes of change. Any natural phenomenon had to have four causes. In order for something to become one of the four Aristotelian causes, one had to be able to place the idea or object in the form of a categorical syllogism to logically show that it was the device of causation. Aristotle's theory of causation broke causes down into four groups: material, formal, efficient, and final. A material cause is what the object consists of, or the starting material. An example of a formal cause is what the object or organism started as and to what it transformed into. The efficient cause entails the direct source of the change, whether it be by human intervention or natural. The final cause is the reason it changed, or the purpose of the change. For example, concerning a soda bottle, the material cause would be plastic, the formal causation would be going from the sheet of plastic to the actual shape of the bottle, the efficient cause would be the maker of the bottle or whoever shaped it, and the final cause would be that it is used to hold a soda or liquid in order for one to drink from it without spilling. These causes further explain the concept that every object and organism has potential being, or what it has the potential to be or become, and actuality, what that object really is. For example, an acorn has the potential to be a tree, but it is actually just a seed. This unique way of observing cause and purpose was not the only way Aristotle observed the universe though.
Aristotle based his theories in sublunar and celestial physics on detailed observations that he made. Aristotle surmised that the universe is actually two different realms, each with their own properties. The terrestrial realm, that is everything under the moon, consisted of the four elements which he used to explain change. Aristotle conjectured that each element had weight, with earth as the heaviest, then water, air, and finally fire being the lightest. Since air and fire were lighter than earth and water, they naturally moved away from the center of the universe, as opposed to earth and water that were naturally drawn toward the center. According to Aristotle, each element had to uniformly encircle the center. Since each element is naturally drawn away or tward the center of the universe, there must be a set of four concentric spheres housing each element. This natural motion of elements allowed Aristotle to realize that the earth is in fact a sphere that rests at the center of the cosmos. For an object to go any other place than where it would naturally go, another force would have to act on it, which Aristotle called violent motion.
Aristotle's work in cosmology went on to explain that the celestial realm, or everything beyond the moon, has a natural circular motion due to its composition. Celestial matter in Aristotle's system was made up of a quintessence or fifth element whose natural motion is uniform circular motion. In his book, On The Heavens, he states: "Further, circular movement is natural to something, it must surely be some simple and primary body which naturally moves with a natural circular motion, as fire moves up and earth down. If, on the other hand, the movement of the rotating bodies about the center is unnatural, it would be remarkable and indeed quite inconceivable that this movement alone should be continuous and eternal, given that it is unnatural. At any rate the evidence of all other cases goes to show that it is the unnatural which quickest passes away" (Aristotle 3). Furthermore, since he had already theorized that the earth was the center of the cosmos, he proposed that the moon orbits around it first. Following the moon, the other celestial bodies moved in circular orbits in the order: Mercury Venus, the sun, Mars Jupiter, and Saturn. Aristotle stated that beyond the orbiting planets there were the fixed stars in a ring around the whole system. Beyond the fixed stars was the "unmoved mover," Aristotle's version of a deity. This deity was not a creator, but simply an indifferent being who set objects in motion without interaction. The Unmoved Mover was also the the final cause of all motion. He did not believe in a creation of the universe, he just believed that humans and the universe have existed and will forever.
Furthermore, definitions of all things, cause and non-cause, came from the creation of categorical classes of objects based on their similar properties. This method of definition is the basis for nearly all taxonomical systems used today in biology, as well as other fields. Aristotle defined all properties as either essential or accidental when it came to objects in the natural world. Essential properties were those that defined the item or organism and didn't change, like wheels on a car or feet on a human being. Accidental properites were properties that were not part of the definition of the organism or object, and did not delineate the object's true identity properties like the color or make of the car or the gender of a human.
The differences between Atomism and Aristotelianism are apparent in some cases but in others no real differences exist at all. The atomists were very fond of the idea of a plurality of worlds. In other words, they theorized the possibility of other worlds besides ours. On the other hand, the Aristotlians believed that there was nothing but the unmoved mover beyond the fixed stars. No life, no other planets or worlds, simply the earth surrounded by a solar system and a fixed set of stars. Aristotle theorized in the elements, essential and accidental properties, definitions or forms, and causation while the atomists went the other direction and used atoms and void as an explanation for creation and materials. Philosophers like Leucippus and Democritus believed in a mostly atheistic world where no deity had anything to do with the rearrangement of the atoms in the void and Aristotle theorized about his unmoved mover as a deistic figure. Atomists believed that both the void and atoms were unlimited, while Aristotle stated that the universe had neither an end or a creation.
Although there were distinct differences between the philosophies of Aristotelians and Atomists, they sought to answer the same questions: how do we come to knowledge? Is there more to life than what we observe with the senses? These pressing questions still plague scientists and philosophers today, but the truth is we may never know the answers. Contextualism aside, the thoughts of the Atomists and Aristotelians are a marvel in their intellectual complexity and depth. Although we have now proven some assumptions of these Greek philosophers false, they nonetheless provided a sturdy base for future inquiries into ontology, epistemology, and the nature of the universe.