The term Presocratics 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. Figure 4.3 A central debate among PreSocratic Greek philosophers concerned whether nature consisted of a single substance—an approach taken by the monists—or was made up of a number of substances—a position taken by the pluralists. One prominent monist, Thales of Miletus, posited that all of nature was made of water. Empedocles, a pluralist, argued instead that the four elements of earth, air, fire, and water formed the basis of the natural world. (attribution: Copyright Rice University, OpenStax, under CC BY 4.0 license) 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 (Figure 4.4). 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. Figure 4.4 For the function y = 1/x, neither x nor y can have a value of zero because y approaches infinity as x approaches zero and x approaches infinity as y approaches zero. Other functions show these same characteristics, which are called asymptotes or limits. (attribution: Copyright Rice University, OpenStax, under CC BY 4.0 license) Video The Paradoxes of Zeno 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. Connections The chapter on metaphysics covers monism and pluralism across cultures. 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.