Module 1 - The Milesians & Heraclitus

Introduction to Ancient Philosophy

Philosophy can be understood in different ways. In everyday use, it often refers to a general outlook on life, a personal creed, or guiding precepts. In this sense, it overlaps with religion and is not restricted to the western tradition. However, in a more restricted sense, the term has roots in ancient Greece, where it was defined as philosophia: love (philo) of wisdom (sophia). For the purposes of this course, philosophy will be studied as a rational method of inquiry, relying on argument, reasoning, and justification.

A central concept in philosophy is logos, a Greek term that means word, speech, argument, account, or reason. It is also the root of many modern disciplines such as psychology, biology, cosmology, geology, and anthropology. Historically, physics, chemistry, and biology were classified as natural philosophy until about a century ago. Even today, the highest academic degree is the Ph.D (Doctor of Philosophy), highlighting this heritage.

The origins of philosophy in the western tradition are closely tied to the origins of science and rational inquiry. While many disciplines have since separated from philosophy, questions about ethics, knowledge, and the nature of reality remain central to philosophical investigation.

Scope of the Course

The course will trace the beginnings of philosophy in ancient Greece over 2,500 years ago. Central figures include Plato (part one) and Aristotle (part two), often regarded as the two giants of classical Greek philosophy. They are famously depicted at the center of Raphael’s School of Athens fresco, with Plato pointing upwards and Aristotle gesturing towards the earth. Surrounding them are figures such as Socrates, Anaximander, Anaxagoras, Heraclitus, and Parmenides, as well as later philosophers including Diogenes, Zeno, Epicurus, and Plotinus.

In part one, the course will cover Plato and his pre-Socratic predecessors. In part two, it will move to Aristotle, the Epicureans, and the Stoics. The study of these thinkers is not about adopting their views wholesale. Rather, it allows for critical engagement: understanding their reasoning, articulating disagreements, and appreciating how their questions and answers shaped intellectual traditions still influential today.

Course Format

Each unit of the course includes short recorded lectures (mostly under ten minutes), assigned readings, and opportunities for discussion on the course boards. Multiple-choice quizzes and short peer-reviewed writing assignments will be available for those pursuing a certificate. Part two of the course will include a final peer-reviewed project. In-video quizzes will appear throughout the lectures but can be skipped. Full details, including requirements and recommended readings, are provided on the course website.

Question: True or false: Philosophy as conceived by the Ancient Greeks was a distinct form of rational inquiry that stressed investigation, justification, and argument.

1. True (correct)
2. False

Explanation: Philosophia (love of wisdom) in the Western tradition is rooted in the exercise of reason and argument in pursuit of truth.

Milesians Readings

Fragments and reports about the Presocratic philosophers:

Thales

Plato, DK11A9, Theaetetus 174a

Why, take the case of Thales, Theodorus. While he was studying the stars and looking upwards, he fell into a pit, and a neat, witty Thracian servant girl jeered at him, they say, because he was so eager to know the things in the sky that he could not see what was there before him at his very feet.

Aristotle, DK11A10, Politics 1259a

Thales, so the story goes, because of his poverty was taunted with the uselessness of philosophy; but from his knowledge of astronomy he had observed while it was still winter that there was going to be a large crop of olives, so he raised a small sum of money and paid round deposits for the whole of the olive-presses in Miletus and Chios, which he hired at a low rent as nobody was running him up; and when the season arrived, there was a sudden demand for a number of presses at the same time, and by letting them out on what terms he liked he realized a large sum of money, so proving that it is easy for philosophers to be rich if they choose, but this is not what they care about.

Aristotle, DK11A22, On the Soul 405a

Thales, too, to judge from what is recorded about him, seems to have held soul to be a motive force, since he said that the magnet has a soul in it because it moves the iron.

Aristotle, DK11A12, Metaphysics 983b

Most of the earliest philosophers conceived only of material principles as underlying all things. That of which all things consist, from which they first come and into which on their destruction they are ultimately resolved, of which the essence persists although modified by its affections—this, they say, is an element and principle of existing things. Hence they believe that nothing is either generated or destroyed, since this kind of primary entity always persists. Similarly we do not say that Socrates comes into being absolutely when he becomes handsome or cultured, nor that he is destroyed when he loses these qualities; because the substrate, Socrates himself, persists.In the same way nothing else is generated or destroyed; for there is some one entity (or more than one) which always persists and from which all other things are generated. All are not agreed, however, as to the number and character of these principles. Thales, the founder of this school of philosophy, says the permanent entity is water (which is why he also propounded that the earth floats on water). Presumably he derived this assumption from seeing that the nutriment of everything is moist, and that heat itself is generated from moisture and depends upon it for its existence (and that from which a thing is generated is always its first principle). He derived his assumption, then, from this; and also from the fact that the seeds of everything have a moist nature, whereas water is the first principle of the nature of moist things.

Aristotle, DK11A14, On the Heavens 294a

Others say the earth rests upon water. This, indeed, is the oldest theory that has been preserved, and is attributed to Thales of Miletus. It was supposed to stay still because it floated like wood and other similar substances, which are so constituted as to rest upon but not upon air. As if the same account had not to be given of the water which carries the earth as of the earth itself!

1.25, Cicero, On the Nature of the Gods

Thales, then, of Miletus, who was the first to inquire into such subjects, said that water was the first principle of things, and that God was the mind that created everything from water. Now if there can be divinity without sensation, why did he mention mind in addition to water? On the other hand, if mind can exist by itself apart from matter, why did he mention water in addition to mind?

Anaximander

203b, Aristotle, Physics

We cannot say that the infinite has no effect, and the only effectiveness which we can ascribe to it is that of a principle. Everything is either a source or derived from a source. But there cannot be a source of the infinite or limitless, for that would be a limit of it. Further, as it is a beginning, it is both uncreatable and indestructible. For there must be a point at which what has come to be reaches completion, and also a termination of all passing away. That is why, as we say, there is no principle of this, but it is this which is held to be the principle of other things, and to encompass all and to steer all, as those assert who do not recognize, alongside the infinite, other causes, such as Mind or Friendship. Further they identify it with the Divine, for it is ‘deathless and imperishable’ as Anaximander says, with the majority of the physicists.

295b, Aristotle, On the Heavens

…but there are some, Anaximander, for instance, among the ancients, who say that the earth keeps its place because of its indifference. Motion upward and downward and sideways were all, they thought, equally inappropriate to that which is set at the centre and indifferently related to every extreme point; and to move in contrary directions at the same time was impossible: so it must needs remain still.

1.25, Cicero, On the Nature of the Gods

Anaximander’s opinion is that the gods have come into being, emerging and disappearing at far distant intervals in the form of innumerable worlds; but how can we conceive of God except as immortal?

Anaximenes

294b, Aristotle, On the Heavens

Anaximenes and Anaxagoras and Democritus give the flatness of the earth as the cause of its staying still. Thus, they say, it does not cut, but covers like a lid, the air beneath it. This seems to be the way of flat-shaped bodies: for even the wind can scarcely move them because of their power of resistance. The same immobility, they say, is produced by the flatness of the surface which the earth presents to the air which underlies it; while the air, not having room enough to change its place because it is underneath the earth, stays there in a mass, like the water in the case of the water-clock. And they adduce an amount of evidence to prove that air, when cut off and at rest, can bear a considerable weight.

365b, Aristotle, Meteorology

We must go on to discuss earthquakes next, for their cause is akin to our last subject….Anaximenes says that the earth breaks up when it grows wet or dry, and earthquakes are due to the fall of these masses as they break away. Hence earthquakes take place in times of drought and again of heavy rain, since, as we have explained, the earth grows dry in time of drought and breaks up, whereas the rain makes it sodden and destroys its cohesion.

Cicero, On the Nature of the Gods Book 1

Anaximenes, who lived later, declared that air was God, that it had come into existence, and that it was unmeasured, infinite, and always in motion; as though air could be God when it is without form, especially when we consider that it is fitting that God should possess not merely some kind of form, but the most beautiful, or as though mortality did not overtake everything that has known a beginning.

Xenophanes

1.28, Cicero, On the Nature of the Gods

Then Xenophanes, who held that the infinite sum of things, combined with mind, constituted divinity, is subject, on the score of mind itself, to the same censure as the others, and to severer censure on the score of infinity, in which there can be no sensation and no connection with anything external.

B12, Sextus Empiricus, Against the Mathematicians 1.289

Homer and Hesiod attributed to the gods all things which are disreputable and worthy of blame when done by men; and they told of them many lawless deeds, stealing, adultery, and deception of each other.

B14, Clement, Miscellanies 5.109

But mortals suppose that the gods are born (as they themselves are), and that they wear man’s clothing and have human voice and body.

B15, Clement, Miscellanies 5.110

But if cattle or lions had hands, so as to paint with their hands and produce works of art as men do, they would paint their gods and give them bodies in form like their own—horses like horses, cattle like cattle.

Source: Hanover Historical Texts Project

Empedocles

Cicero, On the Nature of the Gods 1.29

Empedocles, in addition to many other blunders, goes most discreditably astray in his conception of the gods, for he would have the four natural elements, from which he believes that all things are compounded, to be divine, though it is clear that these come into being, and suffer extinction, and lack all sensation.

Aristotle, Metaphysics 983b

Empedocles, then, differed from his predecessors in that he first introduced the division of this cause, making the source of motion not one but two contrary forces.Further, he was the first to maintain that the so-called material elements are four—not that he uses them as four, but as two only, treating fire on the one hand by itself, and the elements opposed to it—earth, air and water—on the other, as a single nature. This can be seen from a study of his writings.Such, then, as I say, is his account of the nature and number of the first principles.

Aristotle, On Melissus, Xenophanes, and Gorgias, B12 975b1-4

For from what does not exist at all it is impossible that anything come into being, and it is neither possible nor perceivable that being should perish completely; for things will always stand wherever one in each case shall put them.

Aristotle, On Generation and Corruption

Wherefore Empedokles speaks after this manner, saying that nothing comes into being, but there is only mixture and separation of the mixed…But as for Empedokles, it is evident that he holds to genesis and destruction as far as the elements are concerned, but how the aggregate mass of these arises and perishes, it is not evident, nor is it possible for one to say who denies that there is an element of fire, and in like manner an element of each other thing—as Plato wrote in the Timaeos….And some say at once that there are four elements, as Empedokles. But he combines them into two; for he sets all the rest over against fire…Strife then does not separate the elements, but Love separates those which in their origin are before god; and these are gods.

Anaxagoras:

Aristotle, On the Soul 1.2 (404a-405a)

In like manner Anaxagoras says that soul is the moving power, and if any one else has said that mind moved the all, no one said it absolutely as did Demokritos.

Anaxagoras speaks less clearly about these things; for many times he rightly and truly says that mind is the cause, while at other times he says it is soul; for (he says) it is in all animals, both great and small, both honoured and dishonoured. But it is not apparent that what is intelligently called mind is present in all animals alike, nor even in all men.

Anaxagoras seems to say that soul and mind are different, as we said before, but he treats both as one in nature, except that he regards mind especially as the first principle of all things; for he says that this alone of all things is simple and unmixed and pure. And he assigns both to the same first principle, both knowledge and motion, saying that mind moves the all.

Aristotle, Physics 3.4

The physicists, on the other hand, all of them, always regard the infinite as an attribute of a substance which is different from it and belongs to the class of the so-called elements-water or air or what is intermediate between them. Those who make them limited in number never make them infinite in amount. But those who make the elements infinite in number, as Anaxagoras and Democritus do, say that the infinite is continuous by contact-compounded of the homogeneous parts according to the one, of the seed-mass of the atomic shapes according to the other. Further, Anaxagoras held that any part is a mixture in the same way as the All, on the ground of the observed fact that anything comes out of anything. For it is probably for this reason that he maintains that once upon a time all things were together. (This flesh and this bone were together, and so of any thing: therefore all things: and at the same time too.) For there is a beginning of separation, not only for each thing, but for all. Each thing that comes to be comes from a similar body, and there is a coming to be of all things, though not, it is true, at the same time. Hence there must also be an origin of coming to be. One such source there is which he calls Mind, and Mind begins its work of thinking from some starting-point. So necessarily all things must have been together at a certain time, and must have begun to be moved at a certain time.

Aristotle, On the Heavens 3.3

Anaxagoras says the opposite to Empedokles, for he calls the homoeomeries elements (I mean such as flesh and bone and each of those things), and air and fire he calls mixtures of these and of all the other ‘seeds;’ for each of these things is made of the invisible homoeomeries all heaped together. Wherefore all things arise out of these things; for he calls fire and aether the same. And since there is a peculiar motion of every material body, and some motions are simple and some complex, and the complex motions are those of complex bodies and the simple motions of simple bodies, it is evident that there will be simple bodies. For there are also simple motions. So it is evident what elements are, and why they are….Some of those who deny that there is a void say nothing definite concerning lightness and weight, for instance Anaxagoras and Empedokles.

2.7, Aristotle, Meteorology

We must go on to discuss earthquakes next, for their cause is akin to our last subject…Anaxagoras says that the ether, which naturally moves upwards, is caught in hollows below the earth and so shakes it, for though the earth is really all of it equally porous, its surface is clogged up by rain. This implies that part of the whole sphere is ‘above’ and part ‘below’: ‘above’ being the part on which we live, ‘below’ the other.

Cicero, On the Nature of the Gods 1.26

Next Anaxagoras, who derived his system from Anaximenes, was the first to hold that the order and measure of all things was planned and accomplished by the power and intelligence of an infinite mind, in saying which he failed to see that there can be no activity joined with, and allied to, sensation in what is infinite, and no sensation at all in anything that does not feel through its own nature being acted upon.

Democritus and Leucippus

Aristotle, On the Soul 1.3

Some go so far as to hold that the movements which the soul imparts to the body in which it is are the same in kind as those with which it itself is moved. An example of this is Democritus, who uses language like that of the comic dramatist Philippus, who accounts for the movements that Daedalus imparted to his wooden Aphrodite by saying that he poured quicksilver into it; similarly Democritus says that the spherical atoms which according to him constitute soul, owing to their own ceaseless movements draw the whole body after them and so produce its movements. We must urge the question whether it is these very same atoms which produce rest also-how they could do so, it is difficult and even impossible to say. And, in general, we may object that it is not in this way that the soul appears to originate movement in animals-it is through intention or process of thinking.

Aristotle, Physics

Book 1: All thinkers then agree in making the contraries principles, both those who describe the All as one and unmoved (for even Parmenides treats hot and cold as principles under the names of fire and earth) and those too who use the rare and the dense. The same is true of Democritus also, with his plenum and void, both of which exist, be says, the one as being, the other as not-being. Again he speaks of differences in position, shape, and order, and these are genera of which the species are contraries, namely, of position, above and below, before and behind; of shape, angular and angle-less, straight and round.

Book 4: We must begin the inquiry by putting down the account given by those who say that it exists, then the account of those who say that it does not exist, and third the current view on these questions. Those who try to show that the void does not exist do not disprove what people really mean by it, but only their erroneous way of speaking; this is true of Anaxagoras and of those who refute the existence of the void in this way. They merely give an ingenious demonstration that air is something–by straining wine-skins and showing the resistance of the air, and by cutting it off in clepsydras. But people really mean that there is an empty interval in which there is no sensible body. They hold that everything which is in body is body and say that what has nothing in it at all is void (so what is full of air is void). It is not then the existence of air that needs to be proved, but the non-existence of an interval, different from the bodies, either separable or actual-an interval which divides the whole body so as to break its continuity, as Democritus and Leucippus hold, and many other physicists-or even perhaps as something which is outside the whole body, which remains continuous. These people, then, have not reached even the threshold of the problem, but rather those who say that the void exists. They argue, for one thing, that change in place (i.e. locomotion and increase) would not be. For it is maintained that motion would seem not to exist, if there were no void, since what is full cannot contain anything more. If it could, and there were two bodies in the same place, it would also be true that any number of bodies could be together; for it is impossible to draw a line of division beyond which the statement would become untrue. If this were possible, it would follow also that the smallest body would contain the greatest; for ‘many a little makes a mickle’: thus if many equal bodies can be together, so also can many unequal bodies. Melissus, indeed, infers from these considerations that the All is immovable; for if it were moved there must, he says, be void, but void is not among the things that exist. This argument, then, is one way in which they show that there is a void. They reason from the fact that some things are observed to contract and be compressed, as people say that a cask will hold the wine which formerly filled it, along with the skins into which the wine has been decanted, which implies that the compressed body contracts into the voids present in it. Again increase, too, is thought to take always by means of void, for nutriment is body, and it is impossible for two bodies to be together. A proof of this they find also in what happens to ashes, which absorb as much water as the empty vessel. The Pythagoreans, too, held that void exists and that it enters the heaven itself, which as it were inhales it, from the infinite air. Further it is the void which distinguishes the natures of things, as if it were like what separates and distinguishes the terms of a series. This holds primarily in the numbers, for the void distinguishes their nature. These, then, and so many, are the main grounds on which people have argued for and against the existence of the void.

365b, Aristotle, Meteorology

We must go on to discuss earthquakes next, for their cause is akin to our last subject…Democritus says that the earth is full of water and that when a quantity of rain-water is added to this an earthquake is the result. The hollows in the earth being unable to admit the excess of water it forces its way in and so causes an earthquake. Or again, the earth as it dries draws the water from the fuller to the emptier parts, and the inrush of the water as it changes its place causes the earthquake.

Aristotle, Metaphysics 985b

Leucippus, however, and his disciple Democritus hold that the elements are the Full and the Void—calling the one “what is” and the other “what is not.” Of these they identify the full or solid with “what is,” and the void or rare with “what is not” (hence they hold that what is not is no less real than what is, because Void is as real as Body); and they say that these are the material causes of things.And just as those who make the underlying substance a unity generate all other things by means of its modifications, assuming rarity and density as first principles of these modifications, so these thinkers hold that the “differences” are the causes of everything else.These differences, they say, are three: shape, arrangement, and position; because they hold that what is differs only in contour, inter-contact, and inclination (Of these contour means shape, inter-contact arrangement, and inclination position.) Thus, e.g., A differs from N in shape, AN from NA in arrangement, and Z from N in position.As for motion, whence and how it arises in things, they casually ignored this point, very much as the other thinkers did. Such, then, as I say, seems to be the extent of the inquiries which the earlier thinkers made into these two kinds of cause.

Suggested Reading

If you wish to read a more recent translation, consider purchasing Patricia Curd’s A Presocratics Reader: Selected Fragments and Testimonia 2nd edition (Indianapolis: Hackett Publishing 2011).

How We Study the Pre-Socratics

We begin with the group of Greek thinkers known as the Pre-Socratics: Thales, Anaximander, Anaximines, Heraclitus, Parmenides, and Anaxagoras. They lived and wrote in the 6th and 5th centuries BCE, about two and a half millennia ago. Unfortunately, none of their original books have survived. Their works were well-known and influential in their time and for centuries after, but today they exist only in fragments.

The surviving material comes mostly from later quotations and paraphrases. For example, almost everything we know about Thales comes from Aristotle, who lived centuries later. For Anaximander, Anaximines, and others, our information is even more remote, preserved by writers like Hippolytus of Rome, a Christian bishop in the 3rd century CE. His book, The Refutation of All Heresies, was intended to discredit Greek philosophy, yet ironically became a key source for preserving it. Even a hostile witness is still a witness, and historians of philosophy must rely on such sources.

The task of studying the Pre-Socratics is therefore like archaeological reconstruction. Imagine a ruined temple: most of the original structure is gone, pieces have crumbled, and some fragments are scattered across museums like the British Museum. Archaeologists gather these pieces and use both the physical evidence and written reports from earlier travelers to rebuild an image of the temple. Similarly, scholars piece together fragments, quotations, and testimonies to reconstruct lost philosophies.

This project has been ongoing for the past two centuries. Scholars have collected the fragments in sourcebooks, completing the recovery phase. The next step is reassembly. Unlike the temple, however, we do not have all the pieces of the Pre-Socratic texts. Sometimes we have only a few sentences. The reconstruction is therefore a matter of interpretation, hypothesis, and conjecture. Our goal is to take these fragments and try to understand the whole philosophies that once existed.

This is the project we engage in: studying partial evidence, connecting the fragments, and working toward an understanding of entire philosophical systems.