Pre-Socratic Philosophy
(The Com plete Notes)
Thales of Miletu s
In tr oduction to Thales of Miletus
Thales was born in the city of Miletus in Ionia around 685 BCE. He was a well-known
public figure in his day and was included on most lists naming the Seven Sages of
Greece. It seems that his fame was not only due to his theoretical achievements, but also
to more practical triumphs. Among his accomplishments he could count military
engineering (he redirected the flow of a raging river so that King Croessus's army could
cross), geometry (he devised a means of measuring the height of the pyramids and the
distance of ships at sea using triangulation), and astronomy (in 585 BCE., using his
astronomical knowledge along with the Babylonian tables of lunar and solar orbits, he
was the first man to correctly predict a solar eclipse).
Thales also wrote a guide for mariners and managed to amass a fortune by using his
astronomical theories to predict the appearance of a large olive crop and then buying up
all the olive presses in the surrounding area (the sole aim of this latter exploit,
supposedly, was to prove that philosophers can make money if they want to). In between
these various activities Thales also found the time to develop the first known
philosophical system. Unfortunately, no fragments of his original writings have survived
to the present day, and all that we know about his thought boils down to five statements
found in Aristotle. From these five statements we can identify four basic tenets of
Thales' world view:
(1) The world derives from water;
(2) The world rests on water;
(3) The world is full of gods;
(4) Soul produces motion
Aristotle offers up even these snippets very hesitantly, suggesting that even by his time
Thales was known only by report and not through any first-hand evidence.
Th e W or ld Der ives fr om W ater (fr agm en t A12)
With this notion, Thales ushers in the single most important preoccupation of the
Presocratics: the problem of physis. In its most robust form, the physis problem is a
search to identify that thing out of which all else is derived and will ultimately return
(the source or origin of the world), as well as that thing of which everything else is a
variation (the unifier within nature). In Thales', as far as we can tell from the evidence,
,his physis—water—only fulfills the first of these functions. Water is the substance from
which the entire cosmos emerged (and perhaps also to which it will return). Whether or
not it is also the unifier within nature is impossible to determine, since we have no
evidence that bears on the issue. Everything in the world may be a variation on water
according to Thales, or it may not.
The claim that there is a single substance out of which everything else derived is
commonly referred to as material monism: material because it claims that the source of
all nature is something physical (as opposed to, say, something mental), and monism
because it posits that there is only one such thing. Thales is the first of a long line of
material monists, extending all the way to the present day. The notion that the whole
universe emerged from primeval water was a common theory in Near Eastern and Greek
mythology, so Thales' idea is not original in this sense. What is original about the idea,
though, is that Thales' claim is about water as a natural phenomenon and not about
water as some personified god or goddess.
In addition, Thales seems to have provided rational arguments for his water-centric
view. According to Aristotle, Thales turned to biology in order to understand how the
universe was produced. In the biological world he observed three things: first, he
observed that all life depends on water. Give water to a plant and the plant will survive,
remove the water and it will whither and die. This was, similarly, the case for all
animals. Further he observed that seeds, the source of most life, are themselves moist.
Finally, he observed that even heat (in the form of the sun and moon) is generated out of
moisture and kept alive by it (apparently this last bit of data was based on the
relationship he observed between heavenly bodies and the oceans). Observing that life
springs from water in the biological sphere, he concluded that the same must hold true
of the entire universe.
Hippolytus gives another possible line of reasoning that might have convinced Thales.
Water, alone among the natural elements, can take form of a solid, a liquid, or a gas. He
claims that Thales noticed that, "As the water solidifies, things acquire firmness, as it
melts their individual existence in threatened."
What seems most likely is that Thales' first formed the notion of a water-derived world
from the mythological water cosmogonies and that he then turned to these confirming
instances in biology and proto-chemistry for support.
Th e W or ld Rests on W ater (fr agm en t A14)
The notion that the earth floats on water was a commonly held mythological belief, and
it is not clear that Thales' himself held it. Some commentators have argued that the
attribution of this belief to Thales' is the result of confusion about his real claim, which
was that the world derives from water. The question of the world's support, though, is
,one that the other Milesian philosophers address, and so it seems likely that Thales
addressed it as well and that this was his answer.
All Th in gs Ar e Full of Gods (fr agm en t A22)
Thales's claim that all things are full of gods, should not be read as a confirmation of the
mythological idea that the supernatural gods control nature. Instead, we can read this
claim as the natural consequence of the view that all things derive from water. Thales
almost certainly identified water as something divine (all the Presocratics seemed to
identify their physis with divinity), and so everything in the world, as derivatives of
water, would have a divine element to them.
Though Thales believed that water is divine he did not believe that water had human
motivations, wants, desires, or even any interest at all in human society. Water was
probably just divine for him in the sense that it was the source of the universe and
perhaps also in the sense that it was the guiding or controlling force in nature.
additionall The claim that all things are full of gods might also be read as saying
something slightly more substantive than that all things derive from divine water: it
might be read as the claim that even inanimate objects are ensouled or alive in some
sense, perhaps because of their connection to water. In what sense these things should
be seen as alive, becomes clear in the final piece of evidence we have for Thales' thought.
Th e Soul Pr oduces Motion
The claim that the soul produces motion seems to be an attempt to equate being alive, or
having soul, with motive power. Taken together with the previous statement, we might
conjecture that the property of being motive (i.e. being alive) derives from having some
share in divinity (a share which all objects might automatically posses simply because
they derive from water). This would certainly complement theories of some later
Presocratics, including the two other Milesian philosophers who do seem to explicitly
hold that eternal motion is part and parcel of divinity.
Thales, apparently in connection with this statement, pointed as evidence to the case of
magnets. Magnets are inanimate objects, and yet they have the power to move iron. If
even magnets have motive force, he seems to be arguing, then all things probably have
motive force, hence all things are ensouled.
It seems very likely, from the evidence of this example, that the two claims—(1) all
things are full of gods, and (2) the soul produces motion—are connected. Why would
Thales be concerned to prove that inanimate objects have motive force (i.e. are
ensouled) if he did not want to prove that all objects are ensouled? And if he did want to
prove that all objects are ensouled, it seems plausible that this is, at least in part, what
he meant by the claim that all things are full of gods (especially since soul and motive
, power seem to be intimately connected to divinity in the systems put forward by other
Presocratic philosophers).
An axim an der of Miletu s
In tr oduction to An axim an der of Miletus
In all likelihood, Anaximander was the student of Thales. He was born around 610 BCE.,
also in Miletus. Like his teacher, his main interests were in natural philosophy,
geometry, and astronomy. Also like his teacher, he was apparently a very busy figure;
reports tell us that he was the first man to construct a map of the known world, the first
to build a sundial, and the first to build a celestial globe with a chart of the stars.
Anaximander was a material monist, but the physis he posits is much more conceptually
sophisticated than that of Thales. The evidence we have for him provides a slightly more
thorough picture of his thought. Among the many impressive bits and pieces, we can
find the first use of the famous principle of sufficient reason and what appears to be the
first statement of evolutionary theory.
Th e ph ysis Is the Un boun ded
In Thales' system water was supposed to be the source out of which everything arose. In
Anaximander's system the Unbounded (or apeiron) is both the source out of which
everything derives and also the unifier within nature. That is to say, in Anaximander's
worldview, everything in the universe is in fact just a variation on the Unbounded.
As a physis, the Unbounded has many theoretical advantages over water. As
Anaximander no doubt reasoned, the water theory leads to a real problem for the
existence of fire. If everything derived from water (and especially if everything still is
water in some sense), fire could not possibly survive. In order to allow for the existence
of all of the opposites, Anaximander decided to make his physis indefinite, having no
particular qualities of its own. Because the Unbounded is entirely neutral between
opposites, it does not pose a threat to any of them.
This is clearly a major conceptual step forward. Anaximander has separated his
explanatory entity from the entities that need explaining—always a good first step in any
explanatory enterprise. He has posited, in fact, the first theoretical entity—an entity that
we cannot observe, but that whose existence we infer because of its explanatory role.
In addition to being indefinite, the Unbounded is also limitless or infinite, both
temporally and spatially. The Unbounded must be limitless because it must be
inexhaustible in order to give rise to everything else in the universe. It must have
unlimited potentialities.
(The Com plete Notes)
Thales of Miletu s
In tr oduction to Thales of Miletus
Thales was born in the city of Miletus in Ionia around 685 BCE. He was a well-known
public figure in his day and was included on most lists naming the Seven Sages of
Greece. It seems that his fame was not only due to his theoretical achievements, but also
to more practical triumphs. Among his accomplishments he could count military
engineering (he redirected the flow of a raging river so that King Croessus's army could
cross), geometry (he devised a means of measuring the height of the pyramids and the
distance of ships at sea using triangulation), and astronomy (in 585 BCE., using his
astronomical knowledge along with the Babylonian tables of lunar and solar orbits, he
was the first man to correctly predict a solar eclipse).
Thales also wrote a guide for mariners and managed to amass a fortune by using his
astronomical theories to predict the appearance of a large olive crop and then buying up
all the olive presses in the surrounding area (the sole aim of this latter exploit,
supposedly, was to prove that philosophers can make money if they want to). In between
these various activities Thales also found the time to develop the first known
philosophical system. Unfortunately, no fragments of his original writings have survived
to the present day, and all that we know about his thought boils down to five statements
found in Aristotle. From these five statements we can identify four basic tenets of
Thales' world view:
(1) The world derives from water;
(2) The world rests on water;
(3) The world is full of gods;
(4) Soul produces motion
Aristotle offers up even these snippets very hesitantly, suggesting that even by his time
Thales was known only by report and not through any first-hand evidence.
Th e W or ld Der ives fr om W ater (fr agm en t A12)
With this notion, Thales ushers in the single most important preoccupation of the
Presocratics: the problem of physis. In its most robust form, the physis problem is a
search to identify that thing out of which all else is derived and will ultimately return
(the source or origin of the world), as well as that thing of which everything else is a
variation (the unifier within nature). In Thales', as far as we can tell from the evidence,
,his physis—water—only fulfills the first of these functions. Water is the substance from
which the entire cosmos emerged (and perhaps also to which it will return). Whether or
not it is also the unifier within nature is impossible to determine, since we have no
evidence that bears on the issue. Everything in the world may be a variation on water
according to Thales, or it may not.
The claim that there is a single substance out of which everything else derived is
commonly referred to as material monism: material because it claims that the source of
all nature is something physical (as opposed to, say, something mental), and monism
because it posits that there is only one such thing. Thales is the first of a long line of
material monists, extending all the way to the present day. The notion that the whole
universe emerged from primeval water was a common theory in Near Eastern and Greek
mythology, so Thales' idea is not original in this sense. What is original about the idea,
though, is that Thales' claim is about water as a natural phenomenon and not about
water as some personified god or goddess.
In addition, Thales seems to have provided rational arguments for his water-centric
view. According to Aristotle, Thales turned to biology in order to understand how the
universe was produced. In the biological world he observed three things: first, he
observed that all life depends on water. Give water to a plant and the plant will survive,
remove the water and it will whither and die. This was, similarly, the case for all
animals. Further he observed that seeds, the source of most life, are themselves moist.
Finally, he observed that even heat (in the form of the sun and moon) is generated out of
moisture and kept alive by it (apparently this last bit of data was based on the
relationship he observed between heavenly bodies and the oceans). Observing that life
springs from water in the biological sphere, he concluded that the same must hold true
of the entire universe.
Hippolytus gives another possible line of reasoning that might have convinced Thales.
Water, alone among the natural elements, can take form of a solid, a liquid, or a gas. He
claims that Thales noticed that, "As the water solidifies, things acquire firmness, as it
melts their individual existence in threatened."
What seems most likely is that Thales' first formed the notion of a water-derived world
from the mythological water cosmogonies and that he then turned to these confirming
instances in biology and proto-chemistry for support.
Th e W or ld Rests on W ater (fr agm en t A14)
The notion that the earth floats on water was a commonly held mythological belief, and
it is not clear that Thales' himself held it. Some commentators have argued that the
attribution of this belief to Thales' is the result of confusion about his real claim, which
was that the world derives from water. The question of the world's support, though, is
,one that the other Milesian philosophers address, and so it seems likely that Thales
addressed it as well and that this was his answer.
All Th in gs Ar e Full of Gods (fr agm en t A22)
Thales's claim that all things are full of gods, should not be read as a confirmation of the
mythological idea that the supernatural gods control nature. Instead, we can read this
claim as the natural consequence of the view that all things derive from water. Thales
almost certainly identified water as something divine (all the Presocratics seemed to
identify their physis with divinity), and so everything in the world, as derivatives of
water, would have a divine element to them.
Though Thales believed that water is divine he did not believe that water had human
motivations, wants, desires, or even any interest at all in human society. Water was
probably just divine for him in the sense that it was the source of the universe and
perhaps also in the sense that it was the guiding or controlling force in nature.
additionall The claim that all things are full of gods might also be read as saying
something slightly more substantive than that all things derive from divine water: it
might be read as the claim that even inanimate objects are ensouled or alive in some
sense, perhaps because of their connection to water. In what sense these things should
be seen as alive, becomes clear in the final piece of evidence we have for Thales' thought.
Th e Soul Pr oduces Motion
The claim that the soul produces motion seems to be an attempt to equate being alive, or
having soul, with motive power. Taken together with the previous statement, we might
conjecture that the property of being motive (i.e. being alive) derives from having some
share in divinity (a share which all objects might automatically posses simply because
they derive from water). This would certainly complement theories of some later
Presocratics, including the two other Milesian philosophers who do seem to explicitly
hold that eternal motion is part and parcel of divinity.
Thales, apparently in connection with this statement, pointed as evidence to the case of
magnets. Magnets are inanimate objects, and yet they have the power to move iron. If
even magnets have motive force, he seems to be arguing, then all things probably have
motive force, hence all things are ensouled.
It seems very likely, from the evidence of this example, that the two claims—(1) all
things are full of gods, and (2) the soul produces motion—are connected. Why would
Thales be concerned to prove that inanimate objects have motive force (i.e. are
ensouled) if he did not want to prove that all objects are ensouled? And if he did want to
prove that all objects are ensouled, it seems plausible that this is, at least in part, what
he meant by the claim that all things are full of gods (especially since soul and motive
, power seem to be intimately connected to divinity in the systems put forward by other
Presocratic philosophers).
An axim an der of Miletu s
In tr oduction to An axim an der of Miletus
In all likelihood, Anaximander was the student of Thales. He was born around 610 BCE.,
also in Miletus. Like his teacher, his main interests were in natural philosophy,
geometry, and astronomy. Also like his teacher, he was apparently a very busy figure;
reports tell us that he was the first man to construct a map of the known world, the first
to build a sundial, and the first to build a celestial globe with a chart of the stars.
Anaximander was a material monist, but the physis he posits is much more conceptually
sophisticated than that of Thales. The evidence we have for him provides a slightly more
thorough picture of his thought. Among the many impressive bits and pieces, we can
find the first use of the famous principle of sufficient reason and what appears to be the
first statement of evolutionary theory.
Th e ph ysis Is the Un boun ded
In Thales' system water was supposed to be the source out of which everything arose. In
Anaximander's system the Unbounded (or apeiron) is both the source out of which
everything derives and also the unifier within nature. That is to say, in Anaximander's
worldview, everything in the universe is in fact just a variation on the Unbounded.
As a physis, the Unbounded has many theoretical advantages over water. As
Anaximander no doubt reasoned, the water theory leads to a real problem for the
existence of fire. If everything derived from water (and especially if everything still is
water in some sense), fire could not possibly survive. In order to allow for the existence
of all of the opposites, Anaximander decided to make his physis indefinite, having no
particular qualities of its own. Because the Unbounded is entirely neutral between
opposites, it does not pose a threat to any of them.
This is clearly a major conceptual step forward. Anaximander has separated his
explanatory entity from the entities that need explaining—always a good first step in any
explanatory enterprise. He has posited, in fact, the first theoretical entity—an entity that
we cannot observe, but that whose existence we infer because of its explanatory role.
In addition to being indefinite, the Unbounded is also limitless or infinite, both
temporally and spatially. The Unbounded must be limitless because it must be
inexhaustible in order to give rise to everything else in the universe. It must have
unlimited potentialities.
