There is no work by another philosopher which Aristotle refers more to
in the DC than Plato’s Timaeus. The preponderance of references
to his teacher’s dialogue on cosmology should come as no surprise. As the
foundational work in teleological cosmology, the Timaeus is a launch pad for the kind of natural philosophy
Aristotle seeks to develop. Yet, as often in Greek philosophy, debt is the
mother of polemic and Aristotle’s overt treatment of Plato in the DC is predominantly negative. I shall
not here attempt blanket coverage of all the many aspects of the DC’s engagement with Platonic cosmology.[1]
Such a project would require a comprehensive and detailed reading of the DC since the explicit references to the Timaeus are only the tip of the iceberg
of Aristotle’s involvement with that dialogue.
[2]
Instead I wish to characterize the relationship between Aristotle’s cosmology
and the Timaeus by comparing their
scopes and subject matters. I shall do so by focusing, in particular, on what
happens in the DC to one of the most
important principles of Plato’s cosmology, the world soul.
The scope of the DC
The topic of the DC is the
heaven or in Greek ‘ouranos’. There is no need to think that the
Greek title peri ouranou was used by
Aristotle himself.[3]
Nonetheless, the title reflects Aristotle’s own description of the subject
matter as ‘heaven’ in DC I.9 278b11.
In characteristic fashion, however, he points to three different senses of the
word:
‘First, however, we must explain what we mean by ‘heaven’ and in how
many ways we use the word in order to make clearer the object of our inquiry.
In one sense, then, we call ‘heaven’ the substance of the extreme circumference
of the whole, or that natural body whose place is at the extreme circumference.
We recognize habitually a special right to the name ‘heaven’ in the extremity
or upper region, which we take to be the seat of all that is divine. In another
sense, we use this name for the body continuous with the extreme circumference,
which contains the moon, the sun, and some of the stars; these we say are ‘in
the heaven’. In yet another sense we give the name to all body included within
the extreme circumference, since we habitually call the whole or totality ‘the
heaven’. The word, then, is used in three senses.’ (278b9-21)[4]
Is there one of these three senses in which Aristotle primarily meant to
discuss heaven in the DC? The
question exercised the ancient commentators considerably in their attempt to
identify the unitary theme (skopos)
of the work. The disagreement that arose between Simplicius and Alexander on
this question has immediate bearing on the relationship of the DC to the Timaeus.[5]
According to Simplicius, Alexander took the subject matter of the DC to be the ouranos in its third sense, that is to say, the whole world or
cosmos. But if so, Simplicius suggests, its subject matter would be the same as
that of the Timaeus, where Plato
(27b2-3) refers to ‘the whole heaven, or the world (kosmos) or whatever else it might care to be called’. Yet, as
Simplicius points out,
‘Aristotle clearly does not explain the world in this treatise as Plato
did in the Timaeus, where he treated
both of the principles of natural objects, matter and form, motion and time,
and of the general composition of the world, and gave a particular account both
of the heavenly bodies and of those below the moon, in the latter case
occupying himself both with atmospheric phenomena and with the minerals,
plants, and animals on the earth up to and including the composition of man and
his parts’ (3,1.18-23. Transl. Hankinson).
The final words here suggest that Simplicius is thinking of Timaeus 27a5-6, where Critias tells us
that Timaeus’ account will deal with the creation of the heavens (ouranos) ‘down to and including man’. To
obtain Aristotle’s views on the range of issues touched on in the Timaeus we would have to read not only
the DC but also (at least), On Generation and Corruption (for the
composition and interaction of simple bodies), the De Anima (for the nature of soul and its parts), the Meteorology (on geological and
meteorological matters), the Physics
(on the nature of ‘nature’, time, place/space, motion), the Parts, Generation and History of Animals as well as the Parva naturalia (on the composition and
function of animal organs, sexual reproduction, etc.). The Timaeus is a work about the ouranos
in a much more comprehensive sense than the DC.
In terms of its scope, then, the DC
is not cosmology in the sense of the Timaeus.
However, we may also reflect that the border lines between Aristotle’s
works, as we have them, are much less clearly defined than those between most
of Plato’s dialogues. So, whether through the efforts of Aristotle or a later
editor, the work On Generation and
Corruption (GC) at least reads like a continuation of
the end of the DC, whilst the Meteorology, in turn, seems to pick up
from the end of the GC. The DC appears to be part of a series of
interrelated treatises within the area of natural philosophy. Rather than
saying that Aristotle has narrowed the terms of cosmology in relation to Plato
it may therefore be more correct to say that the Timaeus telescopes into one dialogue a range of discussions that
Aristotle develops in much in greater detail throughout a series of contiguous
treatises, one of which is the DC. To
get the full picture of Aristotle’s response to the Timaeus we need to read much more widely than the DC.
However, if the DC does not
cover the same range of topics as the Timaeus,
that may not be because Aristotle does not want to study heaven in the third
sense of ‘the all’, but because he has a different sense of ‘the all’ in mind
from the Platonic cosmos. For notice how Aristotle phrases the third sense of ‘ouranos’: ‘we give the name to all
body included within the extreme circumference, since we habitually call
the whole or totality “the heaven”’ (my emphasis). The phrasing suggests an
emphasis on the body of the universe. If we study the heavens in this sense of
‘the all’ (to pan), we will study the
universe qua all body (to pan sôma). That Aristotle wants to
study the heavens in this sense of the ‘all’ seems to be confirmed by the
opening of the DC. Ch.1 of Book 1 of
the DC introduces the general subject
matter of natural philosophy as ‘bodies and magnitudes and their properties and
movements and the principles of this sort of substance’ (268a2-4). Ch.2 opens
by postponing the question of whether the universe (to pan) is infinite in magnitude or not (a question picked up in
I.5). Instead, Aristotle makes a start on the question about the different
species of its parts. Aristotle explains that we understand such bodies and
magnitudes to be natural insofar as they possess a principle of change: ‘for
nature, we say, is their principle of change’ (268b16). That is why we take all
natural bodies as such to be capable of change of place, in particular (268b14-16).
Aristotle goes on to distinguish three kinds of simple locomotion, up, down and
circular, understood respectively as motion away from the centre, motion
towards the centre, and motion around the centre (268b16-26). The distinction
between these three kinds of simple motion allows Aristotle to distinguish
three kinds of body according to whether it is in their nature to move upwards
(fire and air), downwards (earth and water) or around (aithêr) (268b26-269a6). Fire and air will later be differentiated
by the extent to which they naturally move upwards (fire moves towards the very
extreme universe, air to a place adjacent to that), just as earth and water
will be by the extent to which they move downwards (312b20-313a13).
We are thus given to understand in the first two chapters that the
subject of the DC will be the
universe understood as the totality of bodies or magnitudes and their
characteristic motions and affections. This characterization of the subject
matter seems to contrast in two striking ways with the opening of Timaeus’
account of the cosmos. The first is that Aristotle makes no mention of the
universe’s overall purposefulness, let alone of a purposeful creator. Timaeus,
in contrast, posits as the first principle of the cosmos a creator who wanted
to make the universe as good as possible (29e1-30a3). The universe for Timaeus
was organized not only with a view to making each individual living being as
good as possible but also the whole as good as possible (30c4-31a1). In the Timaeus, in other words, we have cosmic
teleology.
The second difference is that Aristotle does not mention soul. He
describes his subject as body or magnitude and its motions. To be sure,
Aristotle mentions (DC I.1 268a3), as
part of the study of nature, the principles (arkhai) of bodies, which could include soul. Yet, as far at least
as DC I, these principles seem to be
internal to the simple bodies as bodies and do not seem to involve soul.
Timaeus, in contrast, linked the goodness of the cosmos to its possession of
soul. God wanted to make the world as good as possible and therefore he gave it
mind (nous) and therefore also soul (psuchê) (30b1-6). The two points, the
greatest possible goodness of the cosmos and its possession of intelligence and
soul, are here closely related. The soul is the master and ruler of the body
(34c). Thus the motions of the world soul control the orderly motions of the
stars and the planets and ensure that the universe is in the Greek sense of the
word a kosmos, an ordered whole
(40a4-b2). For Timaeus, soul is fundamental to how the cosmos works. Cosmology
is based on psychology.
The omission of the world soul from the first book of the DC therefore suggests a striking
departure both from Platonic cosmology and from Platonic teleology. We should
of course not infer from this omission that Aristotle thereby means to depart
from any kind of teleology. Part of what it means to say that the motion
of each of the five bodies to their proper place is natural is that it moves
towards that place in order to occupy it. The theory of natural motions
is therefore inherently teleological. Yet there is no indication in DC I that there is any role for a soul
or intellect to coordinate the motions of bodies into a well-ordered whole or cosmos in Plato’s sense. The DC seems from the opening resolutely to
be a treatise about the various kinds of simple bodies and the motions that
they naturally, that is, given the kind of body they are, give rise to.
Psychology would seem to be alien to this project.
Aristotle’s cosmology has so far emerged as a more restricted project
than the Platonic precedent in two ways. Firstly, as Simplicius pointed out,
the DC does not pursue cosmology in
the broad way that includes, amongst other matters, the details of how living
beings are put together and work. But secondly, even granting that the DC studies the heavens in the sense of
‘the all’ (to pan), it appears to
focus on the all qua bodily. Related
to this second limitation, the DC
seems to bypass the study of soul and the accompanying cosmic teleology which
were fundamental to Timaean cosmology.
One possible explanation of the difference between Aristotelian and
Platonic cosmology is that in Aristotle nature takes over from soul as an
internal principle of motion and rest. Socrates in the Phaedrus introduced soul as ‘the origin and principle (archê) of motion for other things that
are moved as well (245c8-9). There is a famous interpretative crux relating to
the compatibility of the Phaedrus and
the Timaeus on the question whether all
motion (including the pre-cosmic variety) is caused by soul.[6]
However, it seems clear that soul also in the Timaeus remains a principle (archê)
with the power to move itself and bodies (34b10-35a1, 36e2-4). So Aristotle’s
talk of nature as an inner principle of change and motion, and his ascription
of such natures to inanimate bodies, might seem to be a direct move against
Plato. So one possible answer to the question, what’s happened to Plato’s world
soul in the DC?, is ‘Aristotle
doesn’t need it anymore; the “natures” of the simple bodies do the job of
self-motion.’
However, this comparison between the roles of soul in Plato and nature
in Aristotle may be misleading. On the one side of the comparison, Aristotle is
elsewhere leery of ascribing self-motion in a strict sense to anything other
than animate beings (Physics VIII.4
254b12-255a20). The simple bodies do not properly speaking have self-motion
since they do not have the power to stop themselves and can only move in one
way (255a7-11). So insofar as the DC
suggests that the simple bodies have unqualified self-motion, this suggestion
might be in a contrast not only with the Timaeus
but also with Physics VIII. On the
other side, nothing in the text of the Timaeus
indicates that the simple bodies need soul in order to move.[7]
The simple bodies were originally created by the divine demiurge and in that
sense owe their motions to something external. But once created they move by
necessity in space (chôra) given
their geometrical natures.[8] To
be sure, the world soul may be indirectly involved in their continued
motion. The rotation of the cosmos, which is governed by the world soul (cf.
34b, 36d-e), shakes up the bodies inside, thereby preventing them from staying
in their own proper regions (58a-b). However, the simple bodies by themselves
move towards their proper places without psychic guidance. Indeed, likenesses
of the simple bodies moved towards certain regions (53a) even before the
creation of the cosmos, and so also before the existence of a world soul. If we
enter the necessary qualifications and take into account the Physics, it is not clear that the simple
bodies for Aristotle are self-movers in a significantly stronger sense than in
the Timaeus.
The part of the Timaeus
(47e-69a) that sets out the nature of the simple bodies and their
characteristic motions is sometimes referred to as ‘the works of necessity’.[9]
This part of the dialogue is sandwiched between a part which primarily deals
with the works of reason, and the final part of the dialogue, which, building
on the ‘works of necessity’, develops an account of the functions of human
beings and other animals. The works of necessity are presented as the building
materials and auxiliary causes for the divine craftsmen (68e). The focus in the
middle part of the dialogue is on the physical constituents of the universe,
and the necessary processes and affections that they give rise to. The demiurge
plays a role only in the basic construction of the simple bodies (53b6,
56c3-7), otherwise the bodies are left to interact with each other by their own
devices. The approach to cosmology is here, as one might put it, bottom-up,
whereas in the rest of the Timaeus it
is top-down. Any teleological principle, be it god or world soul, that would
coordinate or organize the various necessary processes into an ordered whole is
therefore missing from the ‘works of necessity’.
It is tempting to insist that our comparison should be between the DC and the ‘works of necessity’
specifically. One might then argue that the limitations of the DC reflect Aristotle’s narrower concern
in this work, shared by Timaeus in ‘the works of necessity’, with the material
building blocks of the universe. This is not to say, of course, that there are
no significant differences between the ways in which Plato and Aristotle
account for the simple bodies. Aristotle’s most fundamental disagreement with
Plato concerns the composition of the simples. Whereas Aristotle analyzes them
in terms of qualities such as hot and cold, wet and dry,[10]
Plato understands their composition geometrically. Aristotle argues that
Plato’s view faces insuperable difficulties. Aristotle argues, for example,
that the geometrical theory cannot account for how the simple bodies change
into one another (III.7 305b27ff.), or for how the different kinds of body come
to have different weights (308b4-28).
These are important differences between the DC and the Timaeus and
Aristotle exploits them to full polemical effect. However, the disagreement
does not concern the role of soul in the motion of the four simple bodies. Both
Aristotle and Plato take it that these bodies move to their proper places of
their own accord. To be sure, Plato does not explain these motions, as does
Aristotle, in terms of the concept of ‘nature’. Yet, as the winnowing basket
analogy implies (Tim. 52e5-53a7), the
motions of the simple bodies to their proper places does express the peculiar
character of each kind of body. Certainly, like the winnowing basket, the
receptacle aids the distribution of the simples, but what ultimately determine
which kind of body ends up where are clearly the bodies’ own properties, just
as the grains in the winnowing basket are distributed in accordance with their
weight. As part of Aristotle’s ongoing polemic in the DC against the Timaeus’
view that the world was created,[11]
he remarks that if the simple bodies moved to their proper places even before
the creation of the world, then their motions must also then have been natural
(i.e. not constrained). But if there were bodies with natures even then, there
must have been a cosmos even then (III.2 300b17). Aristotle thus suggests that
Plato explained the motions of the simple bodies as if they had natures of the
sort that, according to Plato’s own theory, should only exist after the
creation of the world. In other words, Aristotle’s complaint is that Plato
implies that the motion of the simple bodies is caused by their proper natures
even before the simple bodies were supposed to have such natures. We can see in
this objection how close, according to Aristotle, Plato is to helping himself
to something like Aristotle’s own notion of ‘nature’.
The claim that Aristotle’s concept of nature replaces the Platonic soul
as a self-mover is thus misleading as far as the four simple bodies go. Soul
plays no part in explaining how the four simple bodies move to their proper
places in the central part of the Timaeus.
However, the real disagreement about the role of soul in explaining motion
seems to arise when we turn from the sublunary world to the outer heavens.
Again there are certain initial similarities. The shape of the cosmos as a
whole is spherical according to the Timaeus
(33b), while Aristotle chooses the same shape for his cosmos, for parallel
reasons (II.4 286b10-287b21). Both Plato and Aristotle use the sphericity of
the universe in support of the claim that its motion is circular (Timaeus 34a1-2, DC II.6). Both characterize the circular motion of the heavens, and
in particular that of the outer heavens as ‘unceasing’ (apauston, Timaeus 36e4, DC
279b1, cf. sunechês, DC 287a24 ) and uniform (kata tauta, Timaeus 36c2-3, cf. Laws
898a8ff.; homalês, DC 287a24, cf. Phys. 228b15ff, 265b11ff.).[12]
Notwithstanding their parallel descriptions of the outer heavens Plato
and Aristotle seem to disagree about the cause of their motions. Where Plato
takes the heavens to move round because of the world soul, Aristotle takes the
revolution to be brought about by a fifth, or as he sometimes calls it, a
‘first body’ (e.g. 284a30), namely, aithêr.
The outer heavens are composed of this body, which naturally moves round, just
as fire by its nature moves up, and earth moves down (DC I.3). Since, as we saw, none of the other simple bodies require
soul in order to move, it seems that the introduction of the ‘first’ body may
be meant to dispense with the need for a world soul to account for the
revolutions of the heavens.
It is in this vein that Friedrich Solmsen writes:
‘the first body takes over many functions of the Platonic world soul,
but it can also fill the celestial regions in a material sense (which the world
soul cannot do), being at once the stuff of which the heavenly bodies consist
and the cause of their revolutions. Plato erred in identifying the origin and
agent of circular movement. The difference between this movement and
rectilinear ones is not that the former is typical of soul and the latter
movement is performed by bodies, but that the body engaged in the circular
movement is of a superior order, immune to the changes and mutual
transformations to which the others are liable.’[13]
In one way the first body clearly represents an anti-Platonic stance.
Plato takes soul to be both moving and incorporeal. For Plato the motions of
the world soul are not to be understood as the actualization of some bodily
potential. Rather, to go by the account of the soul’s composition in the Timaeus (35a-37c), the world soul seems
to move and move the way it does because it is a mixture of sameness and
difference, mathematically structured. We are told, moreover, that the world
soul was created before the world body (34b-c).[14]
In the Timaeus, there seems therefore
to be a time in the creation of the world when it is both the case that the
soul exists and revolves and that there is no body attached to these
revolutions. Aristotle finds such a view unintelligible. ‘There is no motion’,
he says, ‘without a natural body’ (DC
279a15-6). Motion (kinêsis) is the
actuality of the potential qua
potential (Phys. 201b5-6) and
potentiality implies matter. Once we have identified a peculiar kind of motion
of the heavens it is therefore necessary, at least if this motion is natural,
to find some matter whose potential is actualized in this motion. For Aristotle
aithêr is this matter.
However, the fact that for Aristotle the heavenly revolutions manifest
the natural potential of aithêr does
not by itself mean that these motions are not also a manifestation of soul.
From what we have seen so far, it may come as a surprise that Aristotle does
speak of the outer heavens as animate and alive: ‘since we have already
determined that functions of this kind belong to things which possess a
principle of movement, and that the heaven is animate and possesses a principle
of movement, clearly the heaven must also exhibit above and below’ (DC II.2 285a27-30). Again at DC II.3 286a7-a11 Aristotle implies that
the heavens are animate. He takes it that the heavens are divine and as such
enjoy everlasting life (zôê).
It is for that reason, he suggests, that the heavens are made of a body which
is by nature such as always to move in a circle.
But now we want to know what role soul plays in relation to aithêr when the heavens move round. We
are of course familiar from the De Anima
(cf. e.g. II.2 413a20ff.) with the idea of the soul as a principle of movement
of living beings, an idea that Aristotle seems to be referring to in the
passage just quoted (DC II.2
285a27-30). Yet given that the aithêr
of the heavens itself has the capacity to move round it is unclear what
difference the addition of the world soul makes to its movements. One
possibility is that soul actualizes or triggers aithêr’s natural potential for circular motion. It is fairly clear
that Aristotle in the DC does not
think of soul in relation to aithêr
in this way. It is the nature of aithêr
to move round just as it is the nature of fire to move up if unimpeded (cf. Ph. VIII.4 255b5-12). In the sublunary
world there are possible obstacles to the upward motion of fire but there are
no superlunary obstacles to the revolutionary tendencies of aithêr.[15]
Another, more promising way of thinking of soul’s agency is as a
regulatory cause. Aithêr moves round
of its own accord but soul determines the manner of its revolutions.[16]
We might think of the relationship between soul and aithêr by analogy with the relationship between soul and the fire
within us in nutrition. So in DA II.4
Aristotle explains that:
Fire is in a sense the helping cause (sunaition), but it is certainly not responsible without
qualification. Rather the soul [is responsible]; for the growth of fire is
unlimited (eis apeiron), as long as
there is something that can be burned. But all things constructed naturally
have a limit (peras) and proper
proportion (logos) of magnitude and
growth. And these things are the responsibility of soul, but not of fire, and
of the formula (logos) rather than
the matter. (416a13-18, transl. from M.L.Gill)[17]
Fire contributes as a helping cause, as a sunaition, to nutrition by burning the food. We could even say that
fire is responsible for the fact that the food is burned. Yet it is not fire as
such that is responsible for the way in which the food is burnt, since fire
would continue consuming the food as long as any was available. But there is a
limit or proportion (logos) to the
burning of the food in nutrition, and it is soul which imposes this
limit. The relationship between fire and soul in nutrition suggests the
following analogy with the relationship between aithêr and soul in locomotion. It is aithêr that is responsible for the fact that the heavens move
round, but it is soul that is responsible for the way in which they move round.
More particularly, on this analogy soul imposes a limit or proportion on the
revolutions.
The kind of order imposed by soul on aithêr
will of course be rather different from that imposed by soul on fire in
nutrition since we are now dealing with a different kind of change, locomotion
rather than growth and diminution. However, the passage from DC II.2 quoted above gives a good
example of how the analogy with nutrition would work. Aristotle mentions the
heavens’ soul here because he wants to explain the direction of the heavenly
revolutions. ‘Left and right’, ‘up and down’, ‘front and back’ are for
Aristotle said only with qualification. We can distinguish at least two ways in
which we talk about directions. We talk about right and left, back and front,
and up and down in relation to ourselves as observers. However, in animate
beings, Aristotle claims, we also talk about left and right, up and down
according to functions (erga). Again DA II.4 provides a good example. The
roots of a plant seem to grow down in relation to an observer, as well as in
relation to the universe as a whole. However, in terms of nutrition up is where
the food enters, down where the waste exists. So functionally speaking, for
plants the roots are up. Similarly, Aristotle argues in DC II.2 that we can distinguish up and down and right from left in
locomotion as follows: ‘up is the part from which (hothen) movement originates, the right the part from which (aph’ hou) it proceeds, and the front the
direction in which it is directed (eph’
ho)’ (285a23-4). In functional terms, right is therefore where the heavenly
motion proceeds from. Aristotle distinguishes between a primary and a secondary
heavenly motion. He takes the primary motion to be that of the outer heavens,
the stars. The outer heavens revolve from the right to the left and back to the
right (epi dexia),[18]
and from the top to the bottom. Inside the primary motion, there is also a secondary
motion going from left to right (and back again) to which the planets are
subject. As a result, the functional up and down, and left and right, end up
the opposite of how things appear to an observer in
This functional argument crucially depends on the heavens’ being
animate. It is because the heavens have soul that we can differentiate
directionality by function. Such a
functional account of the heavenly motions may itself be taken to be
teleological: the heavenly motions of the outer planets are organized by soul so
as to move from right to left, from up to down. However, there is further
teleological aspect to the account of the heavenly motions as animate which
introduces a more explicit value judgment. As his biology also shows, Aristotle
takes the right, up and front to be better than their opposites, left,
down and back. For our understanding of the principles of motion DC II.2 284b14 refers us, in particular,
to the Progression of Animals, which
says that the starting point of locomotion is honorable, and that ‘the upper is
more honorable than the lower, the front than the back and the right than the
left’ (706b12-14). Enjoying as they do the best life it is not surprising,
therefore, that the outer heavens display the more honorable motions from right
to left and from up to down, whilst the somewhat inferior planets are also
subject to the inferior motion from left to right.
Plato seems to agree that rotation to the right is better. At 36c6
Timaeus says that the single most rational motion of the Same which governs the
heavenly motions moves ‘to the right (epi
dexia)’.[20]
Moreover, Timaeus like Aristotle makes the revolutions of the seven planets
subject to a further motion in the opposite direction. The less rational circle
of the Different, which moves inside and is governed by the circle of the Same,
is thus divided into seven circles running in different directions at different
speeds (36d2-7). Beyond this it is hard to make clear comparisons between the DC and the Timaeus on the relative speeds and courses of the heavenly bodies.
Aristotle refers such matters to astronomy (DC
II.10 291a31), whilst Timaeus postpones discussion of the details of the
planetary motions to a later occasion (38e). However, the distinction between
the superior motion of the stars ‘to the right’ and the inferior contrary
motion of the planets seems common to both.
So far we have seen Aristotle make use of soul when he wants to explain
the direction of the heavenly revolutions, a phenomenon which was not accounted
for simply by the fact that the heavenly bodies’ are composed of aithêr. Because the heavens have a soul
we can apply to them the functional notion of directionality that we use to
explain animal motion. And when we talk about ‘up and down’, and ‘left and
right’ in functional terms we also led to think of one of each of these pairs
as better and the other as worse. The deployment of soul and that of teleology
go hand in hand.
Aristotle again makes explicit reference to soul in his explanation of
the relative complexity of the motions of the various heavenly bodies. Soul is
brought in to deal with the aporia of
‘why we find the greatest number of movements in the intermediate bodies, and
not rather, in each successive body a variety of movement proportionate to its
distance from the primary motion’ (DC
II.12 291b29-32). The primary motion is here that of the outer heavens, that
is, the stars. The outer heavens move with a single uniform motion, from right
to left to right, as we have seen. We might expect those planets that are
closest to the outer heavens to move in a manner most similar to these; that is
to say, with the fewest number of motions.[21]
Similarly, with Earth at the centre of the universe, we might expect the
motions nearest the Earth, and furthest from the fixed stars, to be the most
complex. Yet, Aristotle claims, the movements of the Sun and the Moon are fewer
than those of some of planets closer to the outer heavens (291b35-292a1).
The aporia is solved,
Aristotle argues, by thinking of the heavenly bodies as animate: ‘We think of
the stars as mere bodies, and as units with a serial order indeed but entirely
inanimate; but we should rather conceive of them as enjoying action (praxis) and life (zoê)’ (292a18-21).[22]
It is tempting to think that Aristotle by ‘we’ here means to reflect not just
on the thinking that generally leads people to the aporia, but also on the wider tendency in the DC (which I noted at the outset of this paper) to treat of the
universe as a mere body. This approach, we are now told, leaves an explanatory
deficit in the account of the heavenly motions. We need the concept of soul to
explain the relative complexity of the various heavenly motions. Each living
being seeks by its actions to achieve their proper good. However, different
kinds of living being pursue this aim in different ways. Higher animals
typically display more complex actions than lower animals, with the exception
of the very highest life-form, which enjoys the good with no effort, like a man
who enjoys good health without need of exercise. At the bottom of the hierarchy are plants,
which ‘perhaps have little action and of one kind only’ (292b7-8). Aristotle
suggests that we should think of the planets’ motions in the same way. The most
complete motion is that of the fixed stars, which is simple and effortless. The
planet furthest from the outer heavens and closest to the Earth have like
plants the fewest actions, whereas those closer to the outer heavens have the
most complex motions, like man and the higher animals. For, Aristotle explains,
‘while it is clearly best for any being to attain the real end (telos), yet, if that cannot be, the
nearer it is to the best the better will be its state’ (292b17-19).
Again in this argument we see the close connection for Aristotle between
the ascription of soul to the heavenly bodies and the teleological explanation
of their motions.[23]
The complexity of their motions is explained by the different actions required
for them to best attain their ends. The possibility and appropriateness of the planets’
engaging in these actions are, in turn, explained by the fact that they have
souls.
For Aristotle, then, we need to say that the heavenly bodies have a soul
and not just a body to explain several things about how they move. The fact
that they are made of aithêr explains
that they move round, but it does not explain how they move round, their
direction or their courses. To explain how they move round in the proper
teleological way, that is to say, in the way that shows why these motions are the best, we need to
think of the heavenly bodies as beings with a soul, which live different kinds
of lives.
It is clear that for Aristotle the soul operates on aithêr’s inherent ability to move round. The aithêr of the heavenly bodies revolves independently of soul, yet
soul can be said to impose a certain form and structure on its revolutions.
Soul can to that extent be thought of as a formal cause of the heavenly motions
with aithêr as the material cause. In
a similar way we saw that whilst fire would burn foodstuff whether or not it
was part of a living being, soul would in nutrition impose a limit and
proportion to the way the fire burned. Soul and aithêr might then with justification be thought of as related as
form to matter in the revolutions of the heavens.
In the Timaeus, meanwhile, the
soul is created separately from the body, inserted into the body from without,
and moves it in a way that seems not to express any inherent potentiality of
body. For Timaeus there is no special body with the natural potentiality to
move round and therefore no special first body, such as aithêr, for the heavenly bodies to be made out of. Rather, the
heavenly bodies, or at least their majority, as Timaeus puts it, are made out
of fire,[24] whose
natural motion is rectilinear,[25]
not circular. When the soul is put in charge (36e3) we might therefore think
that it imposes its circular motions on the body of the universe.
It is for this reason, I take it, that Aristotle gets the impression (DC II.1 284a27) from Plato that the continuous
circular motion of the outer heavens is enforced on the heavenly bodies by
soul:
‘Yet nor is it reasonable that it [the outer heavens] is preserved by
soul constraining (anagkousês) it to
remain everlasting; for such a life of the soul cannot be free from pain or
blessed; since [the soul] is in fact accompanied by force in its movement, if
the soul causes the first body to move when the latter is of a nature to move
otherwise, and cause it to move continuously, then this soul must be without rest
and deprived of all relief of mind (emphronos)’
(284a27-3, Leggatt transl.).
Aristotle seems to have in mind two passages in the Timaeus in particular. Firstly, 34b8-9 where Timaeus describes the
life of the universe as that of a happy god (eudaimona theon), and, secondly, 36e2-5, where Timaeus says that,
when the world soul had been added to the world body, ‘the soul interfused
everywhere from the centre to the circumference of heaven, of
which also she is the external envelopment, herself turning in
herself, began a divine beginning of never ceasing and rational life (emphronos biou) enduring throughout all
time’ (transl. Jowett). Aristotle’s objection is that unless the body that the
soul moves itself has a natural circular motion, soul will have to enforce this
motion on the body. Within the schema Aristotle adopts in DC I.2 any motion that is not natural to a body is unnatural to it.[26]
But Plato does not present the circular motions as natural to the matter of the
heavenly bodies. Aristotle therefore infers that the circular motion must be
unnatural to the heavenly bodies. Soul can then only move the heavenly bodies
round by forcing them to do so, an effort that is inconsistent with its
enjoying a happy and quietus life.[27]
In sum, Aristotle’s objection is to the specific idea that the soul
moves the heavenly bodies by force, an idea which seems to follow from Plato’s
making fire, in particular, the matter of the heavenly bodies.[28]
Aristotle is not objecting to the general idea that there is a soul
which moves the heavens, as some scholars have claimed.[29]
For the idea that the heavens are ensouled is, as we have seen, crucial to
Aristotle’s own teleological explanation in Book II of the direction and
complexity of the heavenly motions.
I have argued in this paper that, despite an emphasis on the bodily
constituents of the universe in the DC,
Plato’s world soul reemerges in the DC
at crucial points where Aristotle wants to offer a certain kind of teleological
explanation of the directions and courses taken by the heavenly motions.
Aristotle’s use of the heavenly soul here looks like a continuation of those
passages in the Timaeus where Plato
accounts for the various revolutions by means of distinctions within the world
soul. For Timaeus, we recall, the heavenly motions of the world soul were the
prime examples of good order in the universe. It is conspicuous that Aristotle
brings in the soul precisely in those contexts where he wants to show that the
heavens move the way they do because that is the best way. Despite their
different views of the composition of the heavenly bodies, it seems that both
Aristotle and Plato would have us believe that the excellence of the heavenly
motions ultimately requires us to think of them as animate.
I have been concerned to show that both Plato and Aristotle use notions
of soul to give teleological accounts of the heavenly motions. Yet, given this
shared background, we can also identify some important differences. We refer to
the soul of the Timaeus as the ‘world
soul’ or the ‘cosmic soul’. This description goes together with the claim that
the cosmos as a whole is a single animal (30d1-31a1, 92c5-9). The soul of the
heavens is, then, the soul of the entire universe. The DC, in contrast, never
treats the universe as a single ensouled being. In the DC the outer heaven, the circle that defines the motions of the
stars is ensouled, leading as it does a blissful and eternal life. We are also
led to believe that the planets each have a soul insofar as they, like humans,
animals and plants, engage in the various kinds of action (praxis) typical of them. However, there is no indication that these
various living beings share a soul that can be described as the world soul, let
alone that that they together constitute a single animal. There is therefore in
the DC no notion either of a soul
that might coordinate all of the activities in the cosmos. That is not to say
that a picture of a world order does not emerge from the DC; it is only to say that there is no world soul that is
responsible for any such order. The absence of a soul for the entire world
seems to go hand-in-hand here with the absence of any explicit cosmic teleology
in the DC.
Secondly, the DC, unlike the Timaeus, makes little or no use of the
world soul to suggest how we should live our lives. Both works present the life
of the outer heavens as a prime case of rationality and happiness. However,
whereas the Timaeus emphatically
tells us to imitate this paradigm so that we may become happier and more
virtuous (39b-c, 42b-e, 47a-c), the DC
stays clear of any such overtly moral messages. We can certainly discern a scala naturae in passages such as DC
II.12, which implies that the simplicity of a stellar life is superior to the
complex endeavors of humans, but Aristotle does not invite us in the DC to imitate the divine, as he does for
example in Nicomachean Ethics X.[30]
Indeed, the DC makes the celestial
life seem distant and hardly attainable for human beings. The complexity of the
human practical life contrasts with the effortless simplicity of the outer
heavens, which are changeless, eternal, and able to enjoy the best and most
independent of lives (DC I.9
279a20-23). The heavens are made of a unique material, ‘something beyond the
bodies that are about us on this earth, different and separate from them’, the
‘superior glory’ of whose nature ‘is proportionate to its distance from this
world of ours.’ (269b14-7). For Timaeus, in contrast, the human soul has the same ingredients (if slightly less pure) and same mathematical structure as the world
soul. Like the world soul, the human soul contains a circle of the Same and a circle of the Different, which move in the
same regular way (41d4-7), or at least they did so until we were embodied (43c7-e4). Our souls spent their early days riding
round the universe on a star (41d9-e3); and even now, each time we succeed at
astronomy, we reproduce in our souls the motions of the heavens. For Timaeus
our lives can, in more senses than one, be heavenly again. Astronomy in the Timaeus offers a divine template for the
ethical life, a notion which Aristotle picks up in his ethics but steers well
clear of in the DC. Here, as on other
subject matters, Aristotle divides what Plato’s cosmology united.
Thomas Johansen, University of
Edinburgh
[1]
While one might sympathize with the ambition of G.S.Claghorn (Aristotle's criticism
of Plato's Timaeus, The Hague 1954) to
overcome the polarization of Aristotle and the Timaeus, too many of his assimilations fail to represent either
philosopher. For comparisons between the Timaeus
and the DC, the reader is better
advised to consult F.Solmsen, Aristotle’s System of the Physical World. A Comparison With His
Predecessors, Ithaca, 1960.
[2] Explicit references include: 280a30, 293b32,
300a1, 300b17, 306b19, 308b4. Often the reference to the Timaeus is simply assumed, see, for example, 299a6ff. (on the
geometrical construction of solids in Timaeus
53c4-56c7) and 305b31-306b2 (on the mutual transformation of by resolution into
planes discussed in Timaeus
56c8-57c6).
[3] Cf. D.J.Allan’s note: ‘Titulus Peri Ouranou nusquam apud ipsum
reperitur; titulum de Caelo et Mundo
ab Arabicis exemplaribus translatum crediderim; nusquam enim in codicibus
Graecis kai kosmou adiectum videmus.’
Aristotelis De Caelo, Oxford 1936,
iii.
[4] Unless otherwise indicated, all translations of
Aristotle are from J.Barnes (ed.), The
Complete Works of Aristotle. The Revised Oxford Translation, Princeton
1985.
[5] Cf. R.J.Hankinson’s introduction to his
translation of Simplicius, On Aristotle’s On the heavens 1.1-4, Ithaca,
N. Y. 2002.
[6] Cf. J.B.Skemp, The Theory of Motion in Plato’s Later Dialogues, Amsterdam 1967.
[7] For the suggestion that the simple bodies in
the pre-cosmos are moved by an irrational soul, cf. Skemp, op.cit.. For an alternative answer, cf. my Plato’s Natural Philosophy, Cambridge 2004, 96
[8] For a full account, cf. Plato’s Natural Philosophy, 95-99, 120-7.
[9] After F.Cornford, Plato’s Cosmology, London 1937.
[10] Cf. DC
III.4 302b30.
[11] Cf., in particular, DC I.10-12.
[12] Cf. Solmsen, op.cit. 238.
[13] Solmsen, op.cit.
291.
[14] For a defence of a literal reading of the
creation story, cf. Plato’s Natural
Philosophy, Ch.4.
[15] So Lindsay Judson argues that, as for as the De Caelo is concerned, ‘[Aristotle]
takes aithêr’s natural capacity for
motion not to be a “dormant” at all, but to be a sufficient explanation of the
sphere’s rotation’ in M.L.Gill and J.G.Lennox (eds), Self-Motion. From Aristotle to Newton, Princeton 1994.
[16] I have been inspired in the following by
Judson, op.cit, 160: ‘The argument of
II.2 may be that, over and above its circularity, the motion of the outermost
sphere has a “structure” or form that cannot be explained by reference to the aithêr but that mirrors, and can be
explained by, the form of the being whose matter the aithêr is. More precisely, the circular motion possesses a
particular direction (which Aristotle analyzes in terms of right/left,
above/below).’
[17] Gill and Lennox (eds), op.cit. 21.
[18] When Aristotle talks of the motion of the stars
as ‘beginning from the right and rotating to the right ‘to the right’ (e)pi\ decia/), we should probably think of this
motion as running counter-clockwise, cf. P.Moraux, Aristote Du Ciel, Paris 1965, xciii, note 5 on the ambiguity of the
expression.
[19] Cf. also DC
II.5 288a2-8.
[20] Note, however, that according to Moraux, op.cit xcv, n.5, the motion epi dexia is taken to run clockwise in
the Timaeus.
[21] Aristotle is thinking here of the number of
interconnecting moving spheres needed in order to produce the observed motion
of a planet. Cf. Leggatt op.cit. 246:
‘a planet’s apparent movement is explained as the resultant of several
movements in the following manner: the planet is fixed to a rotating sphere,
the poles of which are affixed to a second, encompassing and rotating sphere;
this second sphere is in turn attached by its poles to a further sphere, and so
on’.
[22] )All ) h(mei=j w(j peri\
swma/twn au)tw=n mo/non, kai\ mona/dwn ta/cin me\n e)xo/ntwn, a)yu/xwn de\
pa/mpan, dianoou/meqa: dei= d 0 w(j metexon/twn u(polamba/nein pra/cewj kai/
zwh=j. Leggatt translates w(j in 292a30 as ‘as though’, with the implication
that the stars do not in fact have soul. However, linguistically, the parallel
with the first occurrence of w(j (a18)
suggests that we should understand w(j
rather in the sense of ‘as’ or ‘qua’.
We have been thinking of the stars only as bodies so far, now we should also
think of them qua ensouled. The
attribution of soul to the stars is thus made no more counterfactual by the
second use of w(j than the attribution of body to the stars is
by the first use.
[23] Cf. G.E.R.Lloyd, Aristotelian Explorations, Cambridge 1996, 171.
[24] Cf. 40a2-4: tou= me\n qei/ou th\n plei/sthn i)de/an e)k
puro\j a)phrga/zeto, o(/pwj o(/ti lampro/taton i)dei=n te ka/lliston ei)/h. 45b4-5 mentions light as a particularly gentle
sort of fire. However, even if we imagined that the sun were made out of this
kind of fire, this would still not count as a fifth kind of body, like aithêr, but rather as a species of fire.
The claim at Tim. 54c4-6 that there
was a fifth kind of geometrical body on which the demiurge modeled the universe
seems irrelevant here, since the firth body is not mentioned as a material
constituent in the universe.
[25] Cf. Timaeus
43b-c, where the four bodies bombard the circular soul with the six rectilinear
motions.
[26] Cf. DC
I.2 269a30-b13
[27] It may be that Plato sought to anticipate this kind of objection at
34a5, where, even before the introduction of soul into the account, Timaeus
gives a circular motion to the body of the universe as appropriate to its
shape. However, this is presented as the result of demiurge ‘taking away’ (apheilen) the six rectilinear motions
(34a3-5), which one might take to be its natural motions given its composition
of fire, earth, water and air. And Timaeus is talking here about the body of
the universe as a whole rather than that of the heavenly bodies, which is a
rather different matter.
[28] DC II.7 289a17 may contain a reference
to the Timaeus.
[29] Cf. in particular Solmsen 244, n.73: ‘De Caelo II (284a27ff.) includes a
scathing rejection of the notion that a world soul should be responsible for
the eternal duration of the world. To my mind the rejection is unqualified and
unambiguous, and it should not be argued that Aristotle merely protests against
a soul working by ananke. Rather what
he appears to say is that soul, if credited with such a function, would have to
operate by ananke. Elsewhere the same
book (2.285a29) asserts o( ourano\j e)/myuxoj, a
significant statement, no doubt, and yet, in view of its uniqueness, its significance
should not be overworked. It should not be interpreted as saying that the
Cosmos has a soul but merely that it is “alive” (so Guthrie) or “animate”,
which is anything but trivial. To be sure, Aristotle does not otherwise know of
entities that are alive but have no soul, yet we may safely leave the
responsibility for this contradiction to himself.’ I think we are better
advised, if possible, not to ascribe the contradiction to Aristotle. The
question may come down (again) to what we mean by ouranos in the expression o( ourano\j e)/myuxoj. If we mean the outer and inner heavens, the ouranos is clearly ensouled, if we mean the entire cosmos, it is
not. For more on the distinction see below. I tend to agree with Judson, op.cit. 159, n.19, that the reference at
285a29 is to the heavens, though I am not sure that reference is to the outermost
heavenly sphere exclusive.
[30] On Aristotle’s debt to the Timaeus in the Ethics,
see D.Sedley, ‘”Becoming like god”
in the Timaeus and Aristotle’ in T.Calvo and L.Brisson, L. (eds.), Interpreting the Timaeus-Critias, Skt. Augustin 1997: 327-39;
reprinted in revised form as ‘The Ideal of Godlikeness’ in G. Fine (ed.), Plato. Oxford Readings
in Philosophy, Oxford 2000 (in one volume), 791-810.