A History of Western Philosophy

The Cosmos of Inequality

Aristotle and Ptolemy

Remember that our guiding theme in this lecture series is the origin and development of prejudice and inequality. We have already seen how difference becomes hierarchical in Plato’s Great Chain of Being, and how the principles of plenitude and continuity lead to the idea of the best of all possible worlds. The Good is that which is its own masterful identity; the corrupt is that which is ‘mixed race’, or compound and not its own pure, independent, and irreducible self-sufficiency. We have also seen that this is the politics of nature and the nature of politics, and that both are the nature and politics of truth, and the truth of nature and politics.

We will now see how such truth, nature, and freedom shaped the view of the whole cosmos and everything within it. 

First, to understand the design of the cosmos we must understand what Aristotle said of movement in the universe. 

All natural bodies and magnitudes we hold to be, as such, capable of locomotion; for nature, we say, is their principle of movement. But all movement that is in place, all locomotion, as we term it, is either straight or circular or a combination of these two which are the only simple movements. And the reason is [20] that these two, the straight and the circular line, are the only simple magnitudes. Now revolution about the centre is circular motion, while the upward and downward movements are in a straight line, ‘upward’ meaning motion away from the centre, and ‘downward’ motion towards it. All simple motion, then, must be motion either away from or towards or about the centre. This seems to be in exact [25] accord with what we said above: as body found its completion in three dimensions, so its movement completes itself in three forms. (On The Heavens, I.2. 268b11-26)

This determines how all movement in the universe is conceived. 

Is there a logic of mastery or identity here? Upward and downward movement are by definition incomplete and thus will not be self-sufficient, not a complete identity. Circular movement is already complete and self-sufficient. Thus, Aristotle reasons that circular movement is primary, simple and by its own nature self-moving. This, as we have seen is the definition of truth and nature as mastery.  The most simple movement must belong to the most simple body, and the most simple body is that which is purely in-itself, or what is called God, or the Good, or the Prime Mover. Circular movement is eternal. Upward and downward movement, for example, fire upwards and water downwards, are not eternal for they are limited and exhaust themselves, when their movement passes away. 

So, circular movement is perfection. Other movement is natural to different bodies, but is not eternal or simple, and cannot therefore be a first principle, or the eternal truth, of all things. 

From this emerges a most important moment in cosmology. Look at the reasoning in what follows now from Aristotle.

Supposing, then, that there is such a thing as simple movement, and that circular movement is simple, and that both movement of a simple body is simple and simple movement is of a simple body (for if it is movement of a compound it will be in virtue of a prevailing element), then there must necessarily be some simple body which moves naturally and in virtue of its own nature with a circular movement…

Further, this circular motion is necessarily primary. For the complete is naturally prior to the incomplete, and the circle is a complete thing…

From this it is clear that there is in nature some bodily substance other than the formations we know, prior to them all and more divine than they…

On all these grounds, therefore, we may infer with confidence that there is something beyond the bodies that are about us on this earth, different and separate from them; and that the superior glory of its nature is proportionate to its distance from this world of ours. (On The Heavens, 268b27-269b16)

There is something perfect (masterful) and different from the four elements that make up the bodies we see around us, something whose natural movement is circular, and whose perfection requires it to be distant from earth and separate from earth. 

Here is where the difference between the simple and the compound, or the perfect and the imperfect, takes the character of the hierarchy of this world and the other world, or god and people.  Aristotle says,

For all men have some conception of the nature of the gods, and all who believe in the existence of gods at all, whether barbarian or Greek, agree in allotting the highest place to the deity, surely because they suppose that immortal is linked with mortal and regard any other supposition as impossible. If then there is, as there certainly is, anything divine, what we have just said about the primary bodily substance was well said. The mere evidence of the senses is enough to convince us of this, at least with human certainty. For in the whole range of time past, so far as our inherited records reach, no change appears to have taken place either in the whole scheme of the outermost heaven or in any of its proper parts. The name, too, of that body seems to have been handed down right to our own day from our distant ancestors who conceived of it in the fashion which we have been expressing. The same ideas, one must believe, recur in men’s minds not once or twice but again and again. And so, implying that the primary body is something else beyond earth, fire, air, and water, they gave the highest place the name of aether, derived from the fact that it ‘runs always’ for an eternity of time. Anaxagoras, however, misuses this name, taking aether as equivalent to fire.

It is also clear from what has been said why the number of what we call simple bodies cannot be greater than it is. The motion of a simple body must itself be simple, and we assert that there are only these two simple motions, the circular and the straight, the latter being subdivided into motion away from and motion towards the centre. (On The Heavens, I.3. 270b5-31)

We now have everything we need to construct a logical cosmos, one based on first principles using the logic of mastery, the Great Chain of Being, and the perfection of the circle to arrive at the form and shape of the universe. It is, as we will see, a cosmos whose origin lies in a logic of inequality and hierarchy.

I urge you to read all of Book II of On The Heavens. It includes a summary of some of the things we have already looked at, so these should be familiar to you as you read. Here are some of the key sentences:

‘The heaven as a whole neither came into being nor admits of destruction, but is one and eternal, with no end or beginning’ (II. 1, 283b27-8).

‘There is some immortal and divine thing which possesses movement but movement such as has no limit’ (Ii.2. 284a4-5).

‘The shape of the heaven is necessarily spherical’ (II.4 286b10) [because the sphere is to solids what the circle is to planes], and ‘the body that revolves with a circular movement must be spherical’ (II.4. 287a3-4).

‘Stars are at rest and move with the circles to which they are attached’ (II.8. 289b34).

‘The earth must be at the center and immovable … because heavy bodies forcibly thrown quite straight upward return to the point from which they started’ (II.14. 296b21-3).

It is clear then, ‘that the earth does not move and does not lie elsewhere than at the center’ (II.14. 296b24-5).[1]

This all gives rise to the Aristotelian conception of the universe. This time I summarize from the book On The Universe. Note how hierarchy is now much clearer here. This might be because, although this work is included in the Corpus Aristotelicum and reflects the school of Aristotle, it is likely not to be by Aristotle himself. It perhaps shows more fidelity to the Great Chain of Being than Aristotle might have had?

The Universe then is a system made up of heaven and earth and the natural things which are contained in them. But the word is also used in another sense of the ordering and arrangement of all things, preserved by and through God. Of this Universe the centre, which is immovable and fixed, is occupied by the life-bearing earth, the home and the mother of diverse creatures. The upper portion of the Universe, a whole with a fixed upper limit everywhere, the home of the gods, is called Heaven. Heaven is full of divine bodies, which we usually call stars, and moves with an eternal motion, and in one circular orbit revolves in stately measure with all the heavenly bodies unceasingly for ever…

The substance of the heaven and stars we call ether, not because it blazes, [5] owing to its fiery nature (as some explain the word, mistaking its nature, which is very far removed from fire), but because it is in continual motion,1 revolving in a circle, being an element other than the four pure and divine…

Now the number of the fixed stars cannot be ascertained by man, although they move in one surface, which is that of the whole heaven. But the planets fall into seven divisions in seven successive circles, so situated that the higher is always greater than the lower, and the seven circles are successively encompassed by one another and are all surrounded by the sphere containing the fixed stars. The position nearest to this sphere is occupied by the so-called circle of the Shining star, or Saturn; next is that of the Beaming star, which also bears the name of Jupiter; then follows the circle of the Fiery star, called by the names both of Heracles and of Mars; next comes the Glistening star, which some call sacred to Mercury, others sacred to Apollo; after that is the circle of the Light-bearing star, which some call the star of Venus, others the star of Hera; then comes the circle of the Sun, and lastly that of the Moon—and there is the limit of the ether which encompasses the heavenly bodies and the area over which they are [30] ordained to move.

After the ethereal and divine nature, which we declare to be orderly and to be, moreover, free from disturbance, change, and external influence, there follows immediately an element which is subject throughout to external influence and disturbance and is, in a word, corruptible and perishable…

Thus then five elements, situated in spheres in five regions, the less being in each case surrounded by the greater—namely, earth surrounded by water, water by air, air by fire, and fire by ether—make up the whole Universe. All the upper [5] portion represents the dwelling of the gods, the lower the abode of mortal creatures. (from On The Universe chapters 2-3, 391b9-393a5)

By the second century AD this model of the cosmos had become the Ptolemean universe which held sway until (and beyond) Copernicus in the 16th century. As we will see in the next lecture, this was the universe that was part of  medieval Judaism, Islam and Christianity. 


Ptolemy was born in Alexandria in Egypt. His dates were c.100-170 AD, so, over 400 years after Aristotle. He wrote in Greek, but his most famous text, the Almagest―originally called Mathematika syntaxis, and then in Latin, The Great Treatise―finally became known as the Almagest from its translation into Arabic, from al-majisti or the greatest, and then the 12th century translation of this into Latin as Almegestum

Since we are concerned here with the cosmos shaped according to the logic of inequality, we are only going to look at Book 1 where Ptolemy rehearses the Aristotelian principles of the cosmos.[2]

For everything that exists is composed of matter, form and motion; none of these [three] can be observed in its substratum by itself, without the others: they can only be imagined. Now the first cause of the first motion of the universe, if one considers it simply, can be thought of as an invisible and motionless deity; the division [of theoretical philosophy] concerned with investigating this [can be called] ‘theology’, since this kind of activity, somewhere up in the highest reaches of the universe, can only be imagined, and is completely separated from perceptible reality…

In the treatise which we propose, then, the first order of business is to grasp the relationship of the earth taken as a whole to the heavens taken as a whole …

The general preliminary discussion covers the following topics: the heaven is spherical in shape, and moves as a sphere; the earth too is sensibly spherical in shape, when taken as a whole; in position it lies in the middle of the heavens very much like its centre; in size and distance it has the ratio of a point to the sphere of the fixed stars; and it has no motion from place to place …

It is plausible to suppose that the ancients got their first notions on these topics from the following kind of observations. They saw that the sun, moon and other stars were carried from east to west along circles which were always parallel to each other, that they began to rise up from below the earth itself, as it were, gradually got up high, then kept on going round in similar fashion and getting lower, until, falling to earth, so to speak, they vanished completely, then, after remaining invisible for some time, again rose afresh and set; and [they saw] that the periods of these [motions], and also the places of rising and setting, were, on the whole, fixed and the same. 

What chiefly led them to the concept of a sphere was the revolution of the ever-visible stars, which was observed to be circular, and always taking place about one centre, the same [for all]. For by necessity that point became [for them] the pole of the heavenly sphere: those stars which were closer to it revolved on smaller circles, those that were farther away described circles ever greater in proportion to their distance, until one reaches the distance of the stars which become invisible. In the case of these, too, they saw that those near the ever-visible stars remained invisible for a short time, while those farther away remained invisible for a long time, again in proportion [to their distance]. The result was that in the beginning they got to the aforementioned notion solely from such considerations; but from then on, in their subsequent investigation, they found that everything else accorded with it, since absolutely all phenomena are in contradiction to the alternative notions which have been propounded …

if one next considers the position of the earth, one will find that the phenomena associated with it could take place only if we assume that it is in the middle of the heavens, like the centre of a sphere…

[I]t has been so clearly established from the actual phenomena that the earth occupies the middle place in the universe, and that all heavy objects are carried towards the earth.

The Ptolemean cosmos was represented in the following way by Peter Apian in 1539.


This will become the template for the theologies of the three religions of the Book. To understand the working of its hierarchical nature, we will need to explore the concept of ‘emanation’ in our next lecture. 


Aristotle, (1984) ‘On The Heavens,’ and ‘On The Universe,’ in The Complete Works of Aristotle vol. 1, edited by Jonathan Barnes, Princeton, Princeton University Press.

Ptolemy, (1984) Ptolemy’s Almagest, trans. GJ Toomer, London, Duckworth and Co, pp. 35-45.

[1] ‘All who deny that the earth lies at the center think that it revolves about the center’ (II.13. 293b19-20).

[2] From Ptolemy, (1984) Ptolemy’s Almagest, trans. GJ Toomer, London, Duckworth and Co, pp. 35-45.

[3] https://en.wikipedia.org/wiki/Celestial_spheres#/media/File:Ptolemaicsystem-small.png

Also In this Lecture Series


And so, we reach an interesting problem.  There is the

A History of Western Philosophy: Prejudice and Inequality

This series of lectures is an educational resource free to use under the conditions of the Creative Commons licence below. 

Sign up to be notified when the next series is released