The emergence of philosophy is associated not so much with the moment when human beings first began asking questions about the universe as with a transformation in the way they justified their answers. The origins of nature, celestial phenomena, the continuity of life, and the transformation of existing things had all been subjects of human thought long before the development of philosophy. With the early Greek thinkers, however, a new approach to explaining these phenomena began to emerge. The order of the world was no longer understood solely through traditional narratives and divine interventions, but increasingly through intelligible principles, observable relationships, and coherent arguments. Philosophy thus acquired a significance extending beyond the presentation of particular doctrines and became an intellectual activity concerned with investigating the grounds upon which such doctrines could be accepted as true.
The first lecture of Introduction to the History of Philosophy I, delivered by Professor Torsten Wilholt at the Institute of Philosophy of Leibniz University Hannover on October 25, 2013, provides an important framework for understanding this historical transformation in early Greek thought. The intellectual development extending from the Ionian natural philosophers to the Pythagoreans, from Heraclitus to Parmenides and Zeno, and finally to the atomism of Leucippus and Democritus is not merely a history of different answers to the question of what substance constitutes the universe. It is also a history of how observation, abstraction, mathematical relationships, logical necessity, and theoretical explanation gradually acquired a determining role in philosophical thought.
These thinkers cannot be placed within a direct and uninterrupted line of progress. Each began with different problems and developed alternative solutions to aspects of earlier explanations they considered insufficient. Nevertheless, they shared a common intellectual orientation: the conviction that the multiplicity, change, and order of the visible world could be understood not only through sensory impressions but also through conceptual relationships extending beyond those impressions. The emergence of philosophical explanation becomes apparent through the investigation of these relationships.
The Problem of Sources in the History of Philosophy: Fragments and Testimonies
The first difficulty in understanding early Greek philosophy arises from the fact that the original works of its thinkers have largely been lost. The ideas of philosophers before Plato are known primarily through brief quotations and accounts transmitted by later authors. While no writings by Socrates himself have survived, Plato’s dialogues have been preserved to a considerable extent. Socrates and Plato therefore stand at the beginning of a period in the history of philosophy that can be investigated in greater detail through surviving textual sources. It would nevertheless be historically inaccurate to claim that philosophical thought originated with their work.
Much of our knowledge of the early Greek philosophers has been transmitted through Plato and Aristotle. In later periods, authors such as Plutarch, Sextus Empiricus, Diogenes Laërtius, and Simplicius also played important roles in preserving this intellectual heritage. These sources, however, cannot be treated as entirely neutral records. When ancient authors discussed earlier philosophers, they frequently proceeded from their own philosophical problems, selecting passages in order to criticize or support particular positions.
Aristotle’s classification of the early natural philosophers within his investigation of material causes and first principles has profoundly influenced the way these thinkers are understood today. Yet Aristotle’s conceptual framework may not correspond completely to the original problems of every thinker who preceded him. When Thales’ water or Heraclitus’ fire is assigned a particular place within Aristotle’s theory of causes, certain aspects of the original meaning of these doctrines may recede into the background. Historical explanation therefore requires a distinction between the classificatory framework established by a later thinker and the original doctrine under investigation.
The collection The Fragments of the Presocratics, initiated by Hermann Diels and subsequently developed by Walter Kranz, marked an important turning point in the systematic study of this fragmentary heritage. Bringing together quotations, testimonies, and explanations scattered across different ancient sources made it possible to examine and compare the views of early philosophers. Nevertheless, collecting the fragments does not mean that the entire original context of a philosophical doctrine has been recovered.
At this point, the history of philosophy itself becomes a problem of knowledge. Establishing what a thinker said is not identical with explaining what that thinker meant. The reliability of a quotation, the context in which it was transmitted, the historical meanings of its terms, and the influence of later interpretations must be considered together. Studying early Greek philosophy therefore involves not merely learning the ideas of the past, but also questioning how philosophical knowledge can be established on the basis of historical sources.
From Mythos to Logos: Explaining Nature Through Its Own Principles
The emergence of ancient Greek philosophy has traditionally been described as the transition from mythos to logos. This expression refers to a transformation from explanations of the universe and natural phenomena through the actions of divine powers toward explanations based on rational and impersonal principles. However, this transformation should not be understood as a historical rupture in which mythological thought suddenly disappeared and was replaced by a fully developed scientific worldview in the modern sense.
Mythological narratives also offered explanations concerning the origins and order of the world. The difference emerged in the principles upon which explanations were based and in the manner in which they were justified. The early Greek natural philosophers began investigating the causes of events within the structure of nature itself. Explanation thus moved away from the question of which particular god had performed a certain action and toward the problem of the principles according to which things come into being and undergo change.
Within this new intellectual approach, nature was regarded not as a collection of accidental events but as an order accessible to rational investigation. Although the visible world contains different objects and phenomena, one may ask whether they depend upon a common principle. The succession of seasons, the growth of living beings, the transformation of substances, and the coming into being and passing away of things all raise the question of whether a permanent underlying principle exists beneath these changes.
One of the first major concepts of early Greek philosophy, archē, stands at the center of this inquiry. Commonly translated as first principle or origin, the concept does not refer exclusively to what comes first in time. It also concerns the fundamental principle from which things arise and through which their existence and transformation may be explained. The search for an archē is therefore not limited to asking how the world began in the past. It also concerns the basis upon which the multiplicity of existing things can be understood.
The importance of the Ionian natural philosophers does not depend upon whether the principles they selected remain valid according to contemporary physics. Their philosophical innovation consisted in accepting that the world was intelligible and attempting to bring different phenomena under a common explanation. Observation thus ceased to be merely the recording of natural events and became an intellectual basis for reaching more general principles.
Thales: From Observation to a General Principle
Thales of Miletus is traditionally regarded as one of the founding figures of early natural philosophy in the Western philosophical tradition. Much of what is known about him comes from later ancient authors. His association with mathematics, geometry, and astronomy is important for understanding his intellectual position, although the historical reliability of all the achievements attributed to him is not equally certain. Accounts of his calculating the height of pyramids from their shadows and predicting a solar eclipse illustrate how the ancient tradition connected natural investigation with mathematical thought.
According to Aristotle’s account in the Metaphysics, Thales considered water to be the fundamental principle of all things. At first sight, this may appear to be a simple proposition asserting that the universe consists of a single substance. Yet the intellectual movement underlying the explanation is more significant. Aristotle suggests that Thales may have been influenced by observations concerning the importance of moisture in the nourishment of living things, the moist character of seeds, and the relationship between warmth and life. The attempt here is to arrive at a general principle from a range of different phenomena.
This intellectual movement begins with individual observations. The dependence of living beings upon water, the relationship between growth and nourishment and moisture, and the widespread presence of water in nature are not left as unrelated facts. Instead, they are brought together to develop a general explanation according to which water lies at the foundation of life and existing things. What matters is not only whether Thales reached the correct conclusion, but also how the explanation was constructed.
The philosophical significance of observation becomes apparent here. The senses reveal particular phenomena, while reason attempts to establish a common relationship among them. However, the movement from observation to a general principle is not a logically necessary deduction. Different observations do not always lead to one inevitable conclusion. Thales’ approach should therefore be understood not as a fully developed scientific method in the modern sense, but as an early attempt to explain observable multiplicity through a common natural principle.
Thales’ conception of water is thus more than a proposal concerning a primary substance. It represents an early example of observation becoming the foundation of theoretical explanation.
Anaximander: The Explanatory Power of Abstraction
Anaximander carries the investigation of the first principle beyond a particular substance recognizable through the senses and toward a more abstract concept. Unlike Thales, who identified water as fundamental, Anaximander explains the origin of things through the apeiron, the boundless or indeterminate. The philosophical significance of this thought lies in questioning why the first principle should itself be a particular kind of matter.
Water, air, and fire possess specific qualities that distinguish them from other elements. Yet when the origin of all different elements is investigated, the question arises whether the first principle can itself be identical with only one of them. Anaximander’s concept of the apeiron introduces the possibility that the first principle need not be identified with any sensibly determinate element. Explanation no longer rests exclusively upon an observable object; it begins to investigate a more general conceptual condition underlying observable things.
The famous fragment preserved from Anaximander describes coming into being and passing away as processes occurring within a temporal order. The thought, transmitted through Simplicius and translated into English in different ways, may be expressed as follows:
“From whatever things existing things come into being, into those same things their destruction also takes place, according to necessity; for they pay one another penalty and recompense for injustice according to the order of time.”
The precise extent of Anaximander’s original wording within the transmitted passage remains a matter of scholarly discussion. Nevertheless, the statement provides an important indication of how early Greek philosophy approached the relationship between coming into being, destruction, necessity, and time.
The fragment also demonstrates a continuity between mythological and conceptual forms of expression. Terms such as justice, injustice, and punishment, ordinarily associated with human relationships, are employed to describe natural processes of generation and destruction. Yet the presence of these terms does not mean that Anaximander merely repeats a traditional mythological narrative. What becomes prominent is the thought that natural processes occur according to a certain necessity and temporal order, independently of individual intentions.
The importance of Anaximander’s thought lies in the growing explanatory function of abstract concepts. Existing things, time, order, and boundlessness are not individual objects directly presented to the senses; nevertheless, they are used to understand relationships among natural events. Philosophical explanation thus moves beyond immediate sensory observation and develops through conceptual abstraction.
This transformation does not mean that reason becomes wholly independent of observation. Rather, it demonstrates that concepts which cannot themselves be directly observed may be constructed in order to understand observable phenomena within a more general structure.
Anaximenes: Explaining the Mechanism of Change
Anaximenes continues the Milesian search for a first principle while identifying air as the fundamental element. His innovation, however, does not consist merely in replacing water with air. Anaximenes attempts to explain through which processes different material states may arise from the same underlying element. To this end, he employs the concepts of condensation and rarefaction.
The rarefaction or condensation of air is conceived as a mechanism explaining how it acquires different physical qualities. According to the ancient tradition, air becomes fire through rarefaction, while condensation produces wind, cloud, water, earth, and stone. This explanation is not identical with contemporary physical knowledge. Nevertheless, it contains an important intellectual advance: the philosopher does not merely state that different substances originate from a common source, but also attempts to show the process by which their differentiation occurs.
The example of breathing attributed to Anaximenes clarifies the relationship between observation and explanatory mechanism. Air blown through narrowed lips feels cool, whereas air released through a more open mouth feels warmer. This experience was used to investigate the relationship between condensation, rarefaction, and temperature. Although the modern physical explanation of the phenomenon differs, the example shows how an ordinary experience could provide a basis for a general theoretical account in early natural philosophy.
The differences among Thales, Anaximander, and Anaximenes therefore cannot be understood merely as three competing proposals concerning the first principle. Thales emphasizes the identification of a common material foundation through observation; Anaximander considers that foundation through a more abstract concept; and Anaximenes seeks to explain change through a particular mechanism. Through these different approaches, the search for an original principle becomes an increasingly differentiated problem of explanation.
Understanding nature now depends not only upon identifying what it is fundamentally composed of, but also upon explaining how different states arise.
The Pythagoreans: The Discovery of Mathematical Order
The Pythagoreans represent a different direction in the development of explanation within early Greek philosophy. While the Ionian philosophers investigated the fundamental principle of nature through material elements, number, proportion, and mathematical relationships acquired a determining position within the Pythagorean tradition. The central question was no longer simply what substance constitutes existing things, but whether the order of nature could be understood through mathematical relationships.
It is difficult to distinguish with certainty the doctrines of Pythagoras himself from those developed by his followers. The religious, ethical, and philosophical characteristics of the Pythagorean community indicate that its teaching was not originally limited to mathematical investigation. Nevertheless, the association of numbers with the fundamental order of nature remains among the most significant contributions of this tradition to the history of philosophy.
The relationship between musical harmony and numerical ratios provides a particularly clear example of the explanatory power of mathematics. The relationship between the vibrating length of a string and the sound it produces can be expressed through definite mathematical proportions. The association of the octave with the ratio 2:1, the perfect fifth with 3:2, and the perfect fourth with 4:3 demonstrates that harmony experienced through hearing possesses a numerical structure. Mathematics here is not an arbitrary classification imposed upon nature from outside. It provides a means of explaining relationships that become apparent in sensory experience with greater precision.
The philosophical significance of this discovery lies in strengthening the idea that mathematical relationships may be more than abstract arrangements existing only in human thought. Certain natural phenomena can be understood through numerical proportions. Mathematics thus comes to be regarded not merely as an instrument of measurement and calculation, but as a theoretical principle capable of explaining the order of existing things.
The importance the Pythagoreans assigned to the number ten, formed by the sum of the first four natural numbers, and to the numerical arrangement known as the tetractys, demonstrates that mathematical relationships were understood alongside cosmological and symbolic meanings. Nevertheless, the fact that numerical harmony explains certain natural phenomena does not prove that all existing things necessarily consist solely of numbers. The philosophical claims of Pythagoreanism extend from particular findings toward a more comprehensive conception of cosmic order.
The presence of doctrines concerning transmigration of the soul, the immortality of the soul, and purification of life within the Pythagorean tradition also shows that mythological and religious elements did not simply disappear with the emergence of philosophical explanation. Mathematical inquiry and religious conceptions of life could coexist within the same intellectual tradition. Early Greek philosophy therefore cannot adequately be described as a single-directional, uninterrupted progression from mythology toward reason.
The lasting importance of Pythagoreanism lies in its powerful articulation of the possibility that the order of nature can be understood through mathematical relationships. This idea would play a determining role in a broad intellectual tradition extending from Plato’s philosophy to modern natural science.
Heraclitus: The Intelligible Order of Change
The philosophy of Heraclitus places the problem of change at the center of early investigations into nature. Existing things undergo continuous transformation; yet the presence of change does not mean that the world is entirely without order. In Heraclitus’ thought, logos is associated with understanding the common order underlying different events and oppositions.
The river example demonstrates how change and continuity may belong to the same reality. Different waters continually flow over those who step into the same river. Although the water changes, the river remains recognizable as the same river. This statement does not merely seek to establish that everything changes. It calls for an investigation of the relationship between changing elements and the continuity of the whole.
Heraclitus’ statement that war is the father of all things similarly emphasizes the relationship between oppositions and processes of becoming in the world. Night and day, life and death, conflict and harmony cannot be regarded as entirely independent realities. Opposites are related to one another within a particular order.
Within Wilholt’s account of early Greek philosophy, the importance of Heraclitus lies in his refusal to explain being exclusively through an unchanging material foundation. Change ceases to be a secondary appearance requiring explanation and becomes a central problem in understanding the world. This does not mean, however, that change lacks all order. Logos makes it possible to understand changing events within a common relationship.
Heraclitus’ philosophy thus raises the question of whether explanation and immutability must necessarily be identified with one another. The fact that a phenomenon is intelligible does not require every aspect of it to remain unchanged. Order may also exist within change. This thought establishes a philosophical perspective different from the problem of logical necessity that Parmenides would develop.
Parmenides: The Logical Necessity of Being
Parmenides is among the thinkers who decisively transformed the character of explanation in early Greek philosophy. While the Ionian philosophers investigated principles underlying observable change, Parmenides asks under what conditions it is possible to think consistently about being. Within this approach, the question is not merely which principle underlies nature, but whether an explanation can be accepted as logically coherent.
Parmenides’ thought has been preserved through a didactic poem traditionally known as On Nature. The poem recounts a journey in which a goddess explains to the thinker the distinction between truth and the opinions of mortals. This mythological form of presentation coexists with the logical investigation contained in the poem. Parmenides’ philosophy is therefore not an example of a period in which mythological language had been completely abandoned. Nevertheless, the thought underlying the poem investigates the logical conditions upon which genuine knowledge must rest.
The way of truth in Parmenides begins from the recognition that what is, is, and that what is not cannot be thought. The problem here is not simply whether something exists in ordinary language. It concerns how non-being could be thought, known, or established as the foundation of an explanation. If absolute non-being cannot be thought, then claiming that genuine being arises from nothing or passes completely into nothing presents a logical difficulty.
Parmenides’ famous fragment, often translated as “Thinking and being are the same,” must also be considered within this context. The interpretation of the expression remains a subject of philosophical debate. It does not immediately follow that everything human beings think must necessarily exist, or that the mind creates the world. At the center of Parmenides’ inquiry stands the relationship between what thought can genuinely comprehend and the necessary conditions of being.
This conception challenges explanations concerning the generation, destruction, division, and transformation of being. Genuine being cannot arise from absolute non-being or pass entirely into non-being. Parmenides therefore moves toward understanding what is as ungenerated, imperishable, whole, and unchanging. The world of change and multiplicity presented by the senses does not possess the same certainty at the level of truth.
It may nevertheless be incomplete to claim that Parmenides excludes the sensory world from consideration altogether. The presence of an account of the natural world in the section of his poem dealing with mortal opinions leaves open the question of how visible reality may be investigated. Even so, his philosophy powerfully demonstrates that sensory observation and logical necessity need not always lead to the same conclusions.
The major innovation in Parmenides’ thought is that an explanation cannot be regarded as sufficient merely because it corresponds to observable phenomena. It must also be coherent in terms of its own conceptual conditions. Logical necessity thus becomes one of the independent and determining criteria of philosophical inquiry.
Zeno: Proof Through Contradiction
The paradoxes of Zeno of Elea are important examples of reasoning developed in connection with Parmenides’ doctrine of being. Zeno challenges the assumption that motion and multiplicity can be accepted as self-evident features of everyday experience by investigating the logical consequences of these assumptions. The significance of his approach lies less in proposing a new physical principle than in demonstrating difficulties arising from the premises of opposing positions.
In the form of reasoning known as reductio ad absurdum, a proposition is provisionally accepted as true, and its consequences are examined to determine whether they lead to contradiction. If the accepted premises produce inconsistent conclusions, the original position or the assumptions supporting it must be reconsidered. Zeno’s paradoxes of motion are among the earliest and most influential examples of this intellectual procedure in the history of philosophy.
In the paradox of Achilles and the tortoise, the faster runner Achilles attempts to overtake a tortoise that has been given a head start. By the time Achilles reaches the tortoise’s initial position, the tortoise has moved farther ahead. When Achilles reaches that new position, the tortoise has advanced another small distance. If the same reasoning continues, Achilles appears to have to cross an infinite number of intermediate distances in order to catch the tortoise.
Everyday experience demonstrates that a faster runner can overtake a tortoise. The philosophical power of the paradox does not consist in simply denying this observation, but in making the relationship between the continuity of motion and infinite divisibility into a problem. Does the possibility of dividing a distance into infinitely many parts necessarily mean that an infinite amount of time is required to traverse them? What is the relationship between the presence of infinitely many stages and the possibility of completing them within a finite duration?
These questions reveal the difference between observing motion and explaining it conceptually. Modern mathematics can clarify certain aspects of the paradox through the concepts of infinite series and limits. Zeno’s historical importance, however, lies in making the everyday certainty of motion susceptible to logical questioning.
The form of reasoning developed by Zeno also transforms the understanding of justification in philosophical debate. Criticizing a position does not require merely proposing an alternative. One may examine the consequences that follow from the position’s own assumptions. Philosophical explanation thus develops through logical examination as well as observation and theoretical proposals.
The Atomists: Explaining the Visible World Through Invisible Structures
The atomism of Leucippus and Democritus represents another stage in the development of explanatory thinking within early Greek philosophy. The atomists accepted change and multiplicity in the sensory world while also attempting to confront the difficulties generated by Parmenides’ conception of the necessary conditions of being. Their basic solution depended upon an account of the world in which unchanging elements form different combinations and separate from one another.
According to this conception, reality fundamentally consists of atoms and the void. Atoms are conceived as indivisible, ungenerated, and imperishable elements. They differ from one another in shape, position, and arrangement. The coming into being and passing away of observable objects are explained not through the creation or destruction of atoms themselves, but through their different combinations and separations.
This model introduces an important distinction in explaining change. The disappearance of an object from the sensory world does not mean that its fundamental constituents have also ceased to exist. Similarly, the formation of a new object does not require its basic components to emerge from absolute nothingness. The visible unity of an object may change while the elements constituting it retain their continuity.
The relationship between atomism and the Parmenidean conception of being becomes apparent here. While the thought of unchanging fundamental elements is preserved, these elements must be capable of being separated from one another in order to explain movement and multiplicity. Yet movement also requires the recognition of the void. By considering the void as part of reality, the atomists introduce a new conceptual solution to the Eleatic approach according to which what is not cannot be thought in any way.
One of the most significant innovations of atomism is the possibility of employing elements that cannot be directly observed to explain observable phenomena. Atoms cannot be individually seen in sensory experience; nevertheless, the different properties, motions, and transformations of objects are explained through their arrangement. The foundation of explanation is therefore no longer restricted to directly observable objects. A theoretical structure believed to make observable phenomena possible also becomes an object of investigation.
A new relationship between observation and theory is established here. The existence of atoms is not presented as an immediate sensory certainty; their acceptance rests upon the explanatory power of a common structure capable of accounting for numerous phenomena in the visible world. This bears a certain historical resemblance to forms of theoretical explanation developed in modern science. Nevertheless, the atoms of Democritus and the particles of modern atomic physics are not identical theoretical entities. The importance of ancient atomism does not lie in having correctly anticipated the physical structure of contemporary particles, but in proposing that visible reality may be understood through an underlying invisible structure.
The thought of Democritus is not limited to the explanation of nature. Views concerning the material constitution of the soul, human life, and moderation also belong to the atomist tradition. The ideals of tranquility of mind and measured conduct show that the investigation of nature and the evaluation of human life were not treated as entirely separate concerns. Theoretical explanation thus does not merely produce knowledge of the external world; it also enters into relation with philosophical questions concerning human existence.
Why Did Philosophy Begin? Wonder and the Value of Theoretical Knowledge
One striking feature of the development of early Greek philosophy is that these thinkers did not direct their investigations exclusively toward the satisfaction of immediate practical needs. Mathematical knowledge, astronomy, and observation of nature could certainly serve particular technical purposes. Yet the distinguishing character of philosophical inquiry does not lie solely in producing useful results. Investigating why nature exists in a particular form, how change occurs, and under what conditions thought can attain true knowledge can be meaningful in itself, even when no direct practical benefit follows.
Aristotle’s association of the beginning of philosophy with wonder (thaumazein) explains this intellectual attitude. Wonder arises when human beings recognize that the things they encounter are not necessarily self-explanatory. A phenomenon accepted as ordinary in everyday life may become a philosophical problem when its causes are investigated. Why existing things change, how motion is possible, or why mathematical relationships hold in nature are questions that may have no immediate practical purpose but can transform humanity’s understanding of the world.
The story of Thales falling into a well while observing the stars and being laughed at by a Thracian servant illustrates the tension between theoretical thought and the practical demands of everyday life. The philosopher, occupied with celestial phenomena, fails to notice the opening directly before him. The story can be read as a criticism of philosophical investigation becoming detached from ordinary life. Yet it also reveals humanity’s capacity to direct attention beyond immediate practical concerns toward understanding a broader order.
In another account transmitted by Aristotle, Thales uses his astronomical knowledge to anticipate a successful olive harvest and rents olive presses in advance, thereby making a profit. The function of this story is not to demonstrate that philosophical knowledge must generate economic benefits. Rather, it suggests that someone engaged in theoretical investigation is not necessarily incapable of dealing with practical problems and may employ knowledge when desired. The value of philosophy, however, cannot be measured exclusively through such outcomes.
The distinctive character of theoretical inquiry lies in the possibility of pursuing knowledge without a direct practical objective. Human beings do not seek to understand the world solely in order to satisfy their needs. They also wish to know how the world is constituted, what relationships underlie events, and what constitutes a correct explanation.
The emergence of philosophy therefore does not represent the appearance of a form of thought entirely detached from practical life. It marks the development, among human activities, of a mode of inquiry capable of taking truth and explanation as ends in themselves. Observation, abstraction, mathematical relationships, logical examination, and the theoretical explanation of invisible structures constitute different possibilities within this inquiry.
Conclusion
The historical importance of early Greek philosophy lies not in having provided correct answers to every question concerning nature, but in making explanation itself an intellectual problem. The distinction between merely asserting a position and justifying it, the question of how observation should be interpreted, the nature of the reality corresponding to mathematical order, and the acceptability of logically inconsistent explanations became developing areas of philosophical inquiry. The historical movement apparent in Torsten Wilholt’s lecture on early Greek thought demonstrates that philosophy is not merely a collection of successive doctrines. Philosophical thought developed as a tradition of inquiry that, while producing explanations of the world, also questioned the conditions under which those explanations could count as knowledge.
