# The Emergence of Classical Philosophy

## Classical Philosophy


### Learning Objectives

By the end of this section, you will be able to:
1. Evaluate the influence of Egyptian scholarship on classical Greek philosophy.
2. Describe the key ideas of the most influential Greek philosophers.
3. Describe the key ideas of the most influential Roman philosophers.
4. Distinguish between major schools of classical thought.

### Egyptian Origins of Classical Philosophy

The understanding that the roots of classical thought lie, at least in part, in Egypt is as old as the ancient Greeks themselves. In The Histories of Herodotus, the ancient Greek historian Herodotus (c. 484–425 BCE) traces Greek beliefs about the gods, religious practices, and understanding of the natural world to Egypt. Herodotus claimed the ancient Greeks adopted practices and ideas as diverse as solemn processions to temples, the belief in an immortal soul, and the knowledge of geometry and astrology from the Egyptians. Herodotus notes that the people of Heliopolis, one of the largest cities in ancient Egypt, “are said to be the most learned in records of the Egyptians” (Herodotus 1890, 116). Plato spent 13 years in Heliopolis, and Pythagoras (c. 570–495 BCE) studied mathematics in Heliopolis for more than two decades (Boas 1948).

### Egyptian and Babylonian Mathematics

Could Pythagoras have learned, rather than discovered, the “Pythagorean” theorem—the law of relationships between the sides and hypotenuse of a right triangle—in Egypt? Almost assuredly. A Babylonian clay tablet dating to approximately 1800 BCE, known as Plimpton 322, demonstrates that the Babylonians had knowledge not only of the relationship of the sides and hypotenuses of a right triangle but also of trigonometric functions (Lamb 2017). Further, the Rhind Mathematical Papyrus provides evidence that the Egyptians had advanced knowledge of algebra and geometry as early as 1550 BCE, presenting problems that include calculating the volume of cylindrical granaries and the slope of pyramids. The Berlin Papyrus 6619, usually dated between 1800 BCE and 1649 BCE, contains a solution to a problem involving the Pythagorean theorem and evidence that the Egyptians could solve quadratic equations. Pythagoras studied with the priests of Heliopolis more than 1,000 years after these documents were created. It is possible that this Egyptian mathematical knowledge had been lost and that Pythagoras rediscovered the relationship during or after his studies in Heliopolis. However, given what we know now about Greek individuals visiting and residing in Egypt, it seems more likely that he was introduced to the knowledge there. As with mathematics, there are specific philosophical ideas that can be traced back to Egypt. This is particularly the case within metaphysics, the branch of philosophy that studies reality, being, causation, and related abstract concepts and principles.

### Akhenaten’s Metaphysics

In the mid-14th century BCE, Akhenaten became pharaoh in Egypt. Partly in an attempt to undercut the growing power of the priests, Akhenaten abolished all other gods and established Aten, the sun god, as the one true god. Akhenaten held that solar energy was the element out of which all other elements evolved or emanated (Flegel 2018). In proposing this idea, Akhenaten established an unseen divinity responsible for causation. Aten became the one true substance that created the observable world. One hymn reads, “You create millions of forms from yourself, the one, / cities and towns / fields, paths and river” (Assmann [1995] 2009, 154). Although the Egyptian elite quickly reestablished the temples and the practices of the full pantheon of gods after Akhenaten’s death, theological thought incorporated this idea of an all-powerful invisible first cause. This idea evolved, with the phrase “one and the millions” coming to signify the sun god as the soul and the world as its body (Assmann 2004, 189). As you will see later in this chapter, this same concept—a single, invisible, unchanging substance expressing itself through forms to give rise to the material world—is the key principle in Plato’s metaphysics.

### The Egyptian Origins Controversy

Scholars have long puzzled over to what extent the origins of classical thought can be said to lie in Egypt. In recent years, a heated debate has erupted over this question. In the three-volume text Black Athena: The Afroasiatic Roots of Classical Civilization, Martin Bernal, a contemporary American professor specializing in modern Chinese political history, argued that the ancient Egyptians and Phoenicians played a foundational role in the formation of Greek civilization and philosophy. He further claimed that an “ancient model” recognizing the African and Middle Eastern origins of Greece was widely accepted until the 19th century, when it was replaced by a racist “Aryan model” proposing Indo-European origins instead. Mary Lefkowitz, a contemporary professor of classical studies, has famously critiqued Bernal’s work. Lefkowitz’s position is that though it is important to acknowledge the debt the Greeks owe to Egyptian thought, Greek philosophy was not wholly derived from Egypt, nor did Western civilization arise from Africa. A bitter academic war of words has ensued, with Lefkowitz and other prominent scholars noting significant errors in Bernal’s scholarship. Lefkowitz authored Not Out of Africa: How Afrocentrism Became an Excuse to Teach Myth as History in 1997. Bernal responded with Black Athena Writes Back in 2001. This exchange reflects a much broader phenomenon in which academics spar over the accuracy of historical narratives and the interpretation of philosophical ideas, often presenting the issues as ethical questions. By thinking critically about these disagreements, we gain deeper insight not only into the topic of study but also into philosophical and political discourse today.

### Ancient Greek Philosophy

Classical philosophy emerged in ancient Greece, following a procession from what are known as the Presocratics; to the three great philosophers, Socrates (470–399 BCE), Plato (c. 428–347 BCE), and Aristotle (384–322 BCE); and then to later schools of thought, including the Epicureans and Stoics. As is the case with all ancient societies, knowledge of these thinkers is limited by the documentation that has survived. Socrates, for example, wrote down nothing. Rather, Plato wrote dialogues featuring his mentor Socrates engaged in philosophical debate with various individuals in Athens, some of them his fellow citizens and other prominent visitors to the city. The material that has survived from ancient Greece has fueled philosophical discourse for two millennia.

### The Presocratics

The term  is somewhat problematic. At least a few of the thinkers considered part of this school were contemporaries of Socrates and are mentioned in Plato’s dialogues. Foremost among these are the Sophists, traveling teachers of rhetoric who serve as foils for Plato’s philosophers. Plato sought to distinguish philosophers, seekers of truth, from Sophists, whom he regarded as seeking wealth and fame and peddling in fallacious arguments. Indeed, one of the most prominent Sophists, Protagoras, is a main character in the dialogue that bears his name.
Researching the Presocratics is difficult because so little of their work has survived. What we have is fragmentary and often based on the testimony of later philosophers. Still, based on the work that is available, we can characterize the Presocratics as interested in questions of metaphysics and natural philosophy, with many of them proposing that nature consisted of one or more basic substances.
The fragments of the works of these early philosophers that have come down to us focus on metaphysical questions. One of the central debates among the Presocratics is between monism and plurism. Those who think nature consisted of a single substance are called monists, in contrast to pluralists, who see it as consisting of multiple substances. For example, the monist Thales of Miletus thought that the basic element that comprised everything was water, while Empedocles the pluralist sought to show that there were four basic elements (earth, air, fire, and water) that were resolved and dissolved by the competing forces of love and strife.

### Prominent Monists

Presocratic philosophers who sought to present a unified conception of nature held that nature ultimately consists of a single substance. This proposition can be interpreted in various ways. The claim proposed by Thales of Miletus (620–546 BCE) that the basic substance of the universe was water is somewhat ambiguous. It might mean that everything is ultimately made of water, or it might mean that water is the origin of all things. Thales and two of his students, Anaximander and Anaximenes, made up the monist Milesian school. Anaximander thought that water was too specific to be the basis for everything that exists. Instead, he thought the basic stuff of the universe was the apeiron, the indefinite or boundless. Anaximenes held that air was the basic substance of the universe.
Parmenides, one of the most influential Presocratic monists, went so far as to deny the reality of change. He presented his metaphysical ideas in a poem that portrays himself being taken on a chariot to visit a goddess who claims she will reveal the truths of the universe to him. The poem has two parts, “the Way of the Truth”, which explains that what exists is unified, complete, and unchanging, and “the Way of Opinion”, which argues that the perception of change in the physical world is mistaken. Our senses mislead us. Although it might seem to us that Parmenides’s claim that change is not real is absurd, he and his student Zeno advanced strong arguments. Parmenides was the first person to propose that the light from the moon came from the sun and to explain the moon’s phases. In this way, he showed that although we see the moon as a crescent, a semicircle, or a complete circle, the moon itself does not change (Graham 2013). The perception that the moon is changing is an illusion.
Zeno proposed paradoxes, known as Zeno’s paradoxes, that demonstrate that what we think of as plurality and motion are simply not possible. Say, for example, that you wish to walk from the library to the park. To get there, you first must walk halfway there. To finish your trip, you must walk half of the remaining distance (one quarter). To travel that final quarter of the distance, you must first walk half of that (an eighth of the total distance). This process can continue forever—creating an infinite number of discrete distances that you must travel. It is therefore impossible that you arrive at the park. A more common way to present this paradox today is as a mathematical asymptote or limit (). From this point of view, you can never reach point a from point b because no matter where you are along the path, there will always be a distance between wherever you are and where you want to be.

### Prominent Pluralists

Parmenides and Heraclitus (525–475 BCE) held diametrically opposed views concerning the nature of the universe. Where Parmenides saw unity, Heraclitus saw diversity. Heraclitus held that nothing remains the same and that all is in flux. One of his most well-known sayings illustrates this well: “[It is not possible to step twice into the same river]. . . . It scatters and again comes together, and approaches and recedes” (quoted in Curd 2011, 45).
Anaxagoras (500–428 BCE) and Empedocles (494–434 BCE) were substance pluralists who believed that the universe consisted of more than one basic kind of “stuff.” Anaxagoras believed that it is mind, or nous, that controls the universe by mixing and unmixing things into a variety of different combinations. Empedocles held that there were four basic substances (the four elements of air, earth, fire, and water) that were combined and recombined by the opposing forces of love and strife.
Finally, there are the schools of the atomists, who held the view that the basic substance of the universe was tiny, indivisible atoms. For the atomists, all was either atoms or void. Everything we experience is a result of atoms combining with one another.

### Presocratic Theology

The Presocratic philosopher Pythagoras (570–490 BCE) and his followers, known as the Pythagoreans, comprised a rational yet mystical sect of learned men. The Pythagoreans had a reputation for learning and were legendary for their knowledge of mathematics, music, and astronomy as well as for their dietary practices and other customs (Curd 2011). Like Socrates, Pythagoras wrote nothing, so scholars continue to debate which ideas originated with Pythagoras and which were devised by his disciples.
Among the Pythagoreans’ key beliefs was the idea that the solution to the mysteries of the universe was numerical and that these numerical mysteries could be revealed through music. A reminder of their mathematical legacy can be found in the Pythagorean theorem, which students continue to learn in school. Pythagoreans also believed in the transmigration of souls, an idea that Plato would adopt. According to this doctrine, the soul outlives the body, and individuals are reborn after death in another human body or even in the body of a nonhuman animal.
Another important Presocratic philosopher who produced novel theological ideas is Xenophanes (c. 570–478 BCE). Xenophanes, who was fascinated by religion, rejected the traditional accounts of the Olympian gods. He sought a rational basis of religion and was among the first to claim that the gods are actually projections of the human mind. He argued that the Greeks anthropomorphized divinity, and like many later theologians, he held that there is a God whose nature we cannot grasp.

### Socrates and Plato

As Socrates never wrote anything, he is remembered today because thinkers like Plato featured him in their writings. Plato deliberately dramatized the life of his teacher Socrates. One of the key questions of Plato’s scholarship is exactly how many liberties he took in depicting the life of his teacher. Scholars generally agree that the dialogues that Plato wrote early in his career are more faithful to the life of Socrates than later ones. His writings are usually divided into three periods: early, middle, and late.
The early dialogues feature a skeptical Socrates who refuses to advance any doctrines of his own. Instead, he questions his interlocutors until they despair of finding the truth at all. These early dialogues tend to be somewhat short with a simpler composition. One of the dialogues features a young man named Meno who is the pupil of a prominent Sophist. The dialogue focuses on the nature of virtue and whether virtue can be taught. At one point in the dialogue, Meno famously compares Socrates to a torpedofish, a fish similar to a stingray that paralyzes its prey. Socrates does this to his dialogue partners: they begin the discussion believing that they know something and over the course of the dialogue begin to question whether they know anything at all.
Gradually, Plato has Socrates give voice to more positive doctrines. These include what comes to be known as the theory of the forms, a metaphysical doctrine that holds that every particular thing that exists participates in an immaterial form or essence that gives this thing its identity. The invisible realm of the forms differs fundamentally from the changing realm we experience in this world. The invisible realm is eternal, unchanging, and perfect. The material things themselves change, but the immaterial forms remain the same. Consider, for example, the form of a rectangle: four adjacent straight sides that meet at 90-degree angles. You can draw a rectangle, but it is an imperfect representation. The desk or table you are sitting at might be rectangular, but are its edges perfectly straight? How perfect was the instrument that cut the sides? If you nick the edge of a table, then it changes and becomes less like the form of a rectangle. With the doctrine of forms, Plato may be said to combine the metaphysics of Parmenides with that of Heraclitus into a metaphysical dualism.
The philosopher’s task is to access the immaterial realm of the forms and try to convince others of its truth. Plato further believed that if we understand the true nature of virtues like wisdom, justice, and courage, we cannot avoid acting in accordance with them. Hence, rulers of states should be philosopher-kings who have the clearest understanding of forms. Yet philosopher-kings never have perfect knowledge because our understanding is based on a material realm that is always changing. True knowledge is only possible in the abstract realms, such as math and ethics.
In the dialogues, Socrates claims that he was divinely inspired to question prominent citizens of Athens to determine whether their claims to know could be verified. These citizens grow annoyed with Socrates after some years of this treatment, eventually bringing charges against him for corrupting the youth and making the weaker argument appear the stronger. The proceedings of the resulting trial were immortalized in Plato’s , where Socrates presents his defense of his life’s work as a philosopher. The dialogue’s name derives from the Greek apologia, meaning “defense”—Socrates never apologizes for anything! He is found guilty and sentenced to death. Socrates becomes a martyr to philosophy, put to death by the democratic government of Athens.

### Aristotle

During the Middle Ages, people referred to Plato’s most famous pupil Aristotle as simply “the Philosopher.” This nickname is a testament to his enduring fame, as well as to the fact that he was driven by philosophical curiosity to try to understand everything under the sun. The first sentence of his famous work  states, “Philosophy begins in wonder.” He exemplified this claim in his writing. His works ranged widely across all the main areas of philosophy, including logic, metaphysics, and ethics. In addition, he investigated natural philosophy, the fields of study that eventually gave rise to science. Aristotle also researched topics that would today be classified as biology and physics. Stylistically, his work was very different from that of his teacher. While Plato’s work was literary and even dramatic, Aristotle’s writings are presented as lecture.
Plato and his successors were prone to mysticism. It was easy to translate the philosophical theory of the forms into a mystical doctrine in which the forms were known by the mind of God. Aristotle resisted this trend. At the center of Aristotle’s work was his doctrine of the four causes. He believed that the nature of any single thing could be understood by answering four basic questions: “What’s it made of?” (material cause), “What shape does it have?” (formal cause), “What agent gave it this form?” (efficient cause), and, finally, “What is its end goal?” (final cause). Not only can we explain the nature of anything by answering these four basic questions, we can also understand the nature of the universe. Aristotle’s universe is a closed system that is comprehensible to humanity because it is composed of these four causes. Each cause leads to another, until we get to the first cause or prime mover at the head of it all. Somewhat obscurely, Aristotle claims that this first cause is “thought thinking itself.”
In addition to the doctrine of the four causes, it is important to understand Aristotle’s account of the soul. Unlike Plato, who held that the soul is an eternal substance that is reborn in various bodies, Aristotle has a functional conception of the soul. He defined the soul based upon what the soul does. In Aristotle’s understanding, all living things have souls. Plants have a vegetative soul that promotes growth and the exchange of nutrients. The animal soul, in addition to taking in nutrients and growing, experiences the world, desires things, and can move of its own volition. Added to these various functions in humans is the ability to reason.
With the four causes and the functional conception of the soul, we can begin to understand Aristotle’s ethics. Aristotle systematized Plato’s conception of ethics based upon his conception of the self and his four causes. Since everything that exists has a purpose, one of the basic questions for ethics is “What is the purpose of the human being?” After considering such candidates as pleasure and power, Aristotle settles on the answer “happiness” or, more accurately, “eudaimonia.” Rather than a fleeting emotional state, eudaimonia is better understood as “flourishing.” So the question at the heart of Aristotle’s ethics is “How should humans best achieve happiness?” His basic answer is that we achieve eudaimonia by cultivating the virtues. Virtues are habits of character that help us to decide what action is preferable in a particular moment. Cultivating these virtues will helps us to lead a fulfilling life.
It is generally true to say that Plato tended to be more focused on the transcendental world of the forms while Aristotle and his followers were more focused on this worldly existence. They shared a belief that the universe was comprehensible and that reason should serve as a guide to ordering our lives.

### Epicureans

In the wake of the giants of Greek philosophy—Socrates, Plato, and Aristotle—some philosophers turned away from Plato’s ideal forms and toward materialism. In this, they can be seen as furthering a trend already present in the thinking of Aristotle. For Aristotle, there can be no immaterial forms—everything that exists has some material basis, though he allows an exception for his first cause, the unmoved mover.
The Epicureans steadfastly rejected the existence of immaterial forms, unmoved movers, and immaterial souls. The Epicureans, like Aristotle, embraced empiricism, which means that they believed that all knowledge was derived from sense experience. This view was the basis of the revival of empiricism in 18th-century British thought and scientific practice. They espoused an ethical naturalism that held that in order to live a good life we must properly understand human nature. The ultimate goal of life is to pursue pleasure. Despite their disagreements with Plato and, to a lesser extent, Aristotle, the Epicureans agreed with their predecessors that human existence ought to be guided by reason.
The two principal Greek Epicureans were Epicurus himself (341–270 BCE) and his Roman disciple Lucretius (c. 99–55 BCE). Although Epicurus’s views are characterized as hedonistic, this does not mean that he believed that we ought to be indiscriminate pleasure-seekers. Instead, he proposed that people could achieve fulfilling lives if they were self-sufficient and lived free from pain and fear. Of course, complete self-sufficiency is just as impossible as a life utterly free from pain and fear, but Epicurus believed that we should strive to minimize our dependence upon others while limiting the pain in our lives. Epicureans thought that the best way to do this was to retire from society into philosophical communities far from the hustle and bustle of the crowd. Epicurus and Lucretius saw the fear of death as our most debilitating fear, and they argued that we must overcome this fear if we were going to live happy lives.
Lucretius developed Epicurean philosophy in a poem called . This poem discusses ethical ideas, but physics provides its focus. Lucretius adopts a material atomism that holds that things are composed of atoms in motion. Rejecting religious explanations, he argues that the universe is governed by chance and exemplified by these atoms in motion. Although the Epicurean philosophers were critically responding to the work of Plato and Aristotle, it should be evident that they also have antecedents in Presocratic thought. We can see this in their atomism and their religious skepticism, which hearkens back to Xenophanes.

### Roman Philosophy

Just as Hellenistic philosophy developed in the long shadows cast by Plato and Aristotle, Roman philosophy also used these two giants of Greek philosophy as reference points. While Roman philosophical traditions were built upon their Greek forebearers, they developed in a Roman cultural context. Rome began as a republic before becoming an empire, and Roman philosophy was affected by this political transformation. Still, Roman philosophical schools were thoroughly grounded in Greek philosophy, with many Roman philosophers even choosing to write in Greek rather than Latin, since Greek was viewed as the language of scholarship.

### Rhetoric and Persuasion in Politics

Recall that Plato defined philosophy in opposition to sophistry. Whereas the philosopher sought the truth in a dispassionate way using reason as a guide, the Sophist addressing a crowd was indifferent to truth, seeking power and influence by appealing to the audience’s emotions. This harsh critique of rhetoric, which can be defined as the art of spoken persuasion, softened with subsequent philosophers. Indeed, Aristotle wrote a text called Rhetoric in which he sought to analyze rhetoric as the counterpart to philosophy. The tension never disappears entirely, however, and the relationship between philosophy and rhetoric and, more generally, the relationship between philosophy and politics remains a perennial question.
Despite the fact that his ideal statesman was a philosopher, Plato generally sought to keep philosophy distinct from the grubbiness of real politics and was concerned about the messiness of democratic politics in particular. In the Roman political context, this ambivalence becomes less apparent. Examples of philosophers who were also statesmen include Cicero (106–43 BCE) and Marcus Aurelius (121–180 CE). Marcus Aurelius even served as emperor of Rome from 161 to 180 CE. However, as the Roman Republic gave way to the Roman Empire, philosophers shifted inward by focusing on things that were in their control.

### Stoicism

Aristotle held that eudaimonia is worthwhile at least in part because it helps us to better deal with various inevitable misfortunes. The Roman Stoics further developed this idea, proposing four core virtues: courage, justice, temperance, and wisdom. The Stoics were wary of the type of false judgments that might arise from the emotions. They were also uneasy with the loss of control associated with strong emotions, observing that some people can become enslaved to their passions. The Stoics prized rational self-control above everything else. This constant work at maintaining inner freedom epitomizes the Stoic conception of philosophy (Hadot 2002).
The Stoics were systematic philosophers whose writings focused on ethics, physics, logic, rhetoric, and grammar. For the Stoics, the world consists of material bodies in motion, causally affecting each other. Real entities are those capable of causally affecting one another. The Stoic god is a material entity who exists in nature and meticulously manages it, the material first cause of the universe, Aristotle’s unmoved mover incarnated as a material entity. In other words, God is an animating reason that gives life to the universe. Unlike the Christian God who transcends the universe, the Stoic god is found within it, a force immanent to the universe who combines and recombines the four elements into things we can experience because they act upon us and we upon them. Stoicism developed at a time when politics in the Roman world was increasingly seen as something outside individuals’ power to change. So Stoics let politics go. While turning away from politics may indeed promote a tranquil life, it also promotes passivity. Thus, Stoicism reached a conclusion similar to that reached by Daoism, as explored in the chapter on early philosophy.

### Academic Skepticism

Academic Skepticism is another aspect of Roman philosophy that developed out of a tendency found in earlier Greek thought. Recall that Socrates questioned whether we could ever know anything at all. The Academic Skeptics opposed the Stoic claims that sense impressions could yield true knowledge, holding instead that knowledge is impossible. Instead of knowledge, Academic Skeptics articulated the idea of degrees of belief. Things are more or less believable based on various criteria, and this degree of believability is the basis for judgment and action. Disciples of the Greek philosopher Pyrrho (c. 360–270 BCE) held that we had to suspend judgment when it comes to knowledge claims, going so far as to say that we cannot even reliably claim that we cannot know anything. Rather than suspending all judgment, Academic Skeptics sought to demonstrate that knowledge claims lead us to paradoxical conclusions and that one can argue cogently both for and against the same proposition.
The philosopher, orator, and statesman Cicero (106–43 BCE) was the most prominent of the Academic Skeptics. His works provide much of the information we have about the school. He had a decisive influence on Latin style and grammar and was decisive in the introduction of Hellenistic philosophy into Rome. The rediscovery of his work in the 15th century ushered in the European Renaissance.

### Neoplatonism

Plotinus (c. 204–270) led a revival of Plato’s thought in the late Roman Empire that lasted until Emperor Justinian closed Plato’s Academy in 529. Plotinus believed that he was simply an expositor of Plato’s work, but the philosophy he developed, known as Neoplatonism, expanded on Plato’s idea. Neoplatonism arose during a time of cultural ferment in the Roman Empire, incorporating ideas borrowed from sources such as Judaism and early Christianity. The key metaphysical problem in Neoplatonism was accounting for how a perfect God could create a universe that was manifestly imperfect. Plotinus solved this problem by applying ideas similar to Plato’s theory of forms. The perfect, unchanging realm is the one inhabited by God, but creation inhabits the changing realm, which only mirrors forms imperfectly. Plotinus claims that creation emanates from God, but the further one is from this source the less perfect things become.

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Classical Greek philosophy owes much to Egyptian scholarship emanating from Heliopolis, as both Pythagoras and Plato are believed to have studied at that center of learning. Indeed, the Plimpton 332 clay tablet reveals that Babylonian mathematicians knew not only of the Pythagorean theorem of right triangles but also of trigonometric functions. Classical philosophy emerged in ancient Greece with the Presocratics; the three great philosophers Socrates (470–399 BCE), Plato (c. 428–347 BCE), and Aristotle (384–322 BCE); and schools of thought that came after—Epicureans, stoics, and others. From what remains of the works of the Presocratics, they were primarily interested in questions of metaphysics and natural philosophy. Some Presocratics, such as Parmenides, were monists while others, such as Heraclitus, were plurists. Plato advanced a theory of the forms, a metaphysical doctrine that holds that every particular thing that exists participates in an immaterial form or essence that gives this thing its identity. The invisible realm of the forms differs fundamentally from the changing realm we experience in this world. The invisible realm is eternal, unchanging, and perfect. Aristotle’s work centers on his doctrine of the four causes: “What’s it made of?” (material cause), “What shape does it have?” (formal cause), “What agent gave it this form?” (efficient cause), and, finally, “What is its end goal?” (final cause). The four causes can explain nature of all things in this universe, including the universe itself. Aristotle’s universe is a closed system of final causes. Each final cause leads to another, until we get to the first cause or prime mover.

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