HOME - Janux - D2L - Email Wikipedia course web page Vimeo course videos Course materials at iTunes U (optional) Twitter: #ouhoscurator
History of Science Roman - Pantheon

History of Science Online

- Course Info - Time tips - Semester at a glance - Weekly assignments at a glance - Timeline -

LibraryThing: Science in Ancient Mesopotamia Week 6: Roman Science

Cicero, On the Nature of the Gods (1st century B.C.)

| Source page | Hero | Cicero | Lucretius | Pliny the Elder | Ptolemy | Galen | Capella | Basil and Philoponos | Augustine | Boethius | Isidore of Seville | Benedict |

Marci Tullii Ciceronis, De Natura Deorum (On the Nature of the Gods), trans. Francis Brooks (London: Methuen, 1896).
Web Source
Online Library of Liberty
Word count


Cicero's On the Nature of the Gods remained one of the most important sources through the early modern period for Roman natural philosophy. In this work, fictional representatives of Stoic, Epicurean, and Academic (Neoplatonic) philosophical schools engage in a dialogue on natural order, religion and the gods. In the excerpt below, the character Balbus expounds Stoic natural philosophy, which as we will see became one of the most influential schools of natural philosophy for the development of science in the 16th and 17th centuries. By reading Cicero you can gain a better understanding of Stoic cosmology and philosophy.

Study Questions

Consider these questions as you read in order to gauge your understanding of the text. Hint: You may want to print this page and mark the key words and phrases relevant to these questions.

  1. Does Cicero's Stoic speaker conceive of the universe as mechanical clockwork, or as an animated, rational being?
  2. Does Cicero's Stoic speaker point to miracles, or to the regular natural order, as evidence of the divine?
  3. According to the second and third paragraphs excerpted below, what are the qualities of the highest element?
  4. Background for the fourth and fifth paragraphs below:
    Stoic natural philosophy rejected Aristotle's dichotomy between the heavens and the sublunar realms, asserting instead that the same reason and laws govern all of the universe. The heavens were no longer made of a fifth element, but "aether" became understood rather as a more pure form of the fourth element, fire, which circulates between the heavens and the sublunar regions. Consequently, Stoics believed the celestial spheres are fluid, not solid; made of fire, not a crystalline fifth element. Therefore the fixed stars and planets "swim through the aether as fish swim through the sea."


Book III, various excerpts.

1. "And the element which surpasses all these, I mean reason, and if we care to express it by a variety of terms, intelligence, design, reflection, foresight, where did we find, whence did we secure it? Shall the universe possess all other qualities, and not this one which is of most importance? Yet surely in all creation there is nothing nobler than the universe, nothing more excellent and more beautiful. There not only is not, but there cannot even be imagined anything nobler, and if reason and wisdom are the noblest of qualities, it is inevitable that they should exist in that which we acknowledge to be supremely noble. Again, who can help assenting to what I say when he considers the harmonious, concordant, and unbroken connection which there is in things? Would the Earth be able to have one and the same time for flowering, and then again one and the same time in which it lies rough? Or could the approach and departure of the Sun be known, at the time of the summer and winter solstice, by so many objects spontaneously changing? Or the tides of the sea, and of narrow straits, be affected by the rising or setting of the moon? Or the dissimilar movements of the planets be maintained by the one revolution of the whole sky? It would be certainly impossible for these things to come to pass in this way, with such mutual harmony amongst all parts of the universe, if they were not held together by one divine and all-pervading spirit....

2. There is, then, an element which holds together and maintains the entire universe, an element, moreover, which is not without sensation and reason. For it is necessary that every element which is not isolated or simple, but which is joined and linked with something else, should have in itself some ruling principle, as, for instance, mind in the case of man, and in the case of animals something similar to mind, which prompts their desires. In trees, and in things which spring from the earth, the ruling principle is supposed to be placed in their roots. By ruling principle I mean the principle which the Greeks call pneuma, which cannot but hold, and which ought to hold, the highest place in each genus. Consequently the thing in which the ruling principle of the whole of nature is contained, must in the same way be the most perfect of all, and the most worthy of power and dominion over all existence. Now we see that in parts of the universe (for there is nothing in the entire universe which is not a part of the whole), sensation and reason exist. These qualities must therefore exist, and exist more vividly and to a greater extent, in that part in which the ruling principle of the universe resides. Consequently the universe must be intelligent, and the element which holds all things in its embrace must excel in perfection of reason; the universe, therefore, must be divine, and so must the element by which the whole strength of the universe is held together. This fiery glow which the universe possesses is also far purer, clearer, and nimbler, and on that account better fitted to arouse sensation, than this heat of ours, by which the objects known to us are preserved and made strong. Since, then, men and animals are maintained by this heat, and through it possess motion and sensation, it is absurd to say that the universe is without sensation, when it is maintained by a burning heat which is unmixed, and free, and pure, and at the same time in the highest degree vivid and nimble, especially considering that the heat which belongs to the universe is moved by itself and its own action, and is not stirred by anything distinct from itself, or by impact from outside. For what can be mightier than the universe, so as to act upon and set in motion the heat by which the universe is to be held together?"

3. I see nothing by which I should sooner satisfy this preconception and idea of ours than by pronouncing, firstly, this universe itself, which nothing can surpass in excellence, to be animate and divine. Here let Epicurus jest as he will (he is not very well suited to the part, and savours but little of his country), and let him declare himself unable to understand what a round and whirling deity is like: for all that he will never move me from this position, which is one that even he himself admits. For he does believe in the existence of gods on the ground that there must necessarily be some exalted nature, which nothing transcends in excellence. Now there is certainly nothing more excellent than the universe, and it is undoubted that that which is animate, and possesses feeling, and reason, and intelligence, is more excellent than that which is without these qualities. It is thus proved that the universe is animate, and that it is endowed with feeling, intelligence, and reason, and hence the conclusion that the universe is divine. These facts will, however, be recognised more easily a little later on from the actual working of the universe.

4. This constancy, then, among the stars, this marked agreement of times through the whole of eternity, though the movements are so various, I cannot understand as existing without mind and reason and forethought, and since we find that these qualities are possessed by the heavenly bodies, we cannot but assign to those bodies themselves their place among the number of divine beings. Nor indeed are what are called the fixed stars without indications of the same intelligence and foresight. Their revolution is a daily one, and is uniform and constant; their movement is neither caused by the æther, nor, as most writers say in their ignorance of natural science, is it bound up with the movement of the heavens. For the æther is not of such a nature as to envelop the stars and to urge them along by its own force; being rare, and transparent, and suffused with equable heat, it does not seem very well adapted for keeping them in place. The fixed stars have, then, a sphere of their own, which is distinct from the pervading æther, and free. Their movements, which are never-ending and unbroken, and marked by a wonderful and incredible harmony, make it so clear that a divine force and intelligence are resident in them, that the man who did not perceive that these very bodies are possessed of the force of divine beings would seem incapable of perceiving anything at all. In the heavens, then, there is no chance, irregularity, deviation, or falsity, but on the other hand the utmost order, reality, method, and consistency. The things which are without these qualities, phantasmal, unreal, and erratic, move in and around the earth below the moon, which is the lowest of all the heavenly bodies. Any one, therefore, who thinks that there is no intelligence in the marvellous order of the stars and in their extraordinary regularity, from which the preservation and the entire well-being of all things proceed, ought to be considered destitute of intelligence himself.

5. But if the things which the earth maintains by means of roots owe their life and vigour to the handiwork of nature, surely the earth itself is maintained by the same power, seeing that after it has been impregnated by seed it produces and puts forth from itself all things, nourishes and increases their roots by its embrace, and is in turn nourished itself by the elements above which are external to it. Its own exhalations also nourish the air, æther, and everything on high. If, then, nature upholds and invigorates the earth, there is the same principle of action in the rest of the universe. For, while roots cleave to the earth, living things are sustained by being breathed upon by air, and it is air which aids us in seeing, hearing, and producing sound, for none of these things can be done without air. In fact it even aids us in movement, since wherever we go and wherever we move, it seems, as it were, to give way and yield. The substances, moreover, which are carried towards the centre of the universe, which is its lowest part, and upwards from the centre, and by a circular revolution round the centre, make the nature of the universe one and continuous. It is made continuous by the substances, of which there are four kinds, changing one into another, water being formed from earth, air from water, and æther from air, and in the reverse order again air from æther, water from air, and earth, which in position is the lowest, from water. In this way by the passage up and down, and backwards and forwards, of these elements, of which all things are composed, the connection of the parts of the universe is maintained. This connection must either be eternal, under the same form as this which we behold, or at any rate of very considerable duration, lasting on for a long and almost immeasurable time. Taking whichever view you please, it follows that the universe is administered by nature. For the sailing of a fleet, the arrangement of an army, or, to again compare the works of nature, the generating of a vine or tree, the figure, moreover, and formation of limbs of a living creature do not indicate so much skill on nature’s part as the universe itself. Either, then, there is nothing which is ruled by sentient nature, or it must be acknowledged that the universe is so ruled. How, indeed, can that which contains all other forms of nature and their seeds, fail to be itself administered by nature? If any one were to say that teeth, and the hair which is a sign of puberty, were created by nature, but that the man himself, in whom they were created, was not formed by nature, he would similarly fail to understand that the things which produce something from themselves possess a more perfect nature than the thing produced.

Additional excerpts:

6. And in the first place let us note the earth as a whole, which is situated in the central quarter of the universe, and is solid, spherical, gathered at every point into that shape by its own gravity, and clothed with flowers, herbs, trees, and fruits, the incredible multitude of all these being set off by a variety which cannot tire. Add to them the cool perennial springs, the liquid transparency of the rivers, the green covering of the banks, the vast hollows of the caves, the rugged rocks, the lofty overhanging mountains, and the boundless plains; add, too, the hidden veins of gold and silver, and the limitless wealth of marble. And what tribes of animals, there are, both tame and wild, and how various! what flights and songs of birds, what grazing of cattle, what forms of woodland life! How shall I next speak of the race of men, the appointed cultivators, as it were, of the earth, who neither allow it to become the lair of savage beasts, nor to be turned into a waste by a rough undergrowth, and whose handiwork makes bright the fields and islands and coasts, dotting them with houses and cities? If we could see these things with our eyes, as we can with our mind, no one, when he gazed upon the earth in its completeness, would doubt as to the divine intelligence. How beautiful, once more, is the sea! how glorious its appearance as a whole! what a number and variety of islands! what delightful shores and coasts! how numerous and dissimilar are the tribes of sea-creatures, some keeping to the depths, some floating and swimming, and some attached by their own shells to the rocks! The sea itself yearns for the earth, and the way in which it plays upon the shore makes it seem as though the two elements had been fused into one. Next to and adjoining the sea is air, which shows the contrast of day and night. Sometimes it expands, and rarefies, and mounts upward, sometimes it thickens, and is gathered into cloud, and by forming moisture fertilises the earth with showers, and sometimes by streaming to and fro it produces wind. It is, moreover, the cause of the yearly fluctuations of cold and heat, and it supports also the flight of birds, and through being inhaled with the breath nourishes and sustains the animate creation.

7. There remains, farthest and highest from our own dwelling place, and surrounding and enclosing all things, the belt of sky, which is also called æther,—the outermost edge and boundary of the universe, within which the fiery bodies take in so marvellous a manner their prescribed and ordered course. Of these the sun, which far exceeds the earth in size, revolves round the earth itself; by its rising and setting it causes day and night, and in its alternate approach and withdrawal it makes each year a double return in opposite directions from its extreme points; during the interval which is marked by these returns it is at one time contracting, so to speak, the earth’s face with gloom, and at another turning it to gladness, so that earth and sky seem to have been made joyful together. The moon, whose area, as mathematicians show, is more than the half part of the earth’s, moves over the same tract as the sun, but is sometimes drawing near to it, and sometimes turning from it; the light which it has received from the sun it sends upon the earth, and it has itself different gradations of light; at one time, moreover, when it is beneath the sun, and between it and the earth, it obscures the sun’s rays and brightness, at another, when it is in opposition with the sun, it comes itself under the shadow of the earth, and is suddenly eclipsed owing to the barrier and interposition of the earth. The wandering stars, as we call them, move round the earth in the same tract, and rise and set in the same way; their course sometimes quickens, sometimes slackens, and is often even brought to a standstill. No sight can be more marvellous or more beautiful. Next there comes the vast multitude of the fixed stars, whose grouping has been so arranged that their resemblance to familiar objects has found them names, and the way in which their constellations have been marked out indicates the presence of divine skill in these great designs.


"Shoot for the moon. Even if you miss, you'll land among the stars." -- Les Brown

University of Oklahoma logo

HSCI 3013. History of Science to 17th centuryCreative Commons license
Kerry Magruder, Instructor, 2004
Brent Purkaple, TA

Report typos or broken links

Go to this course at

spellcheck.net | wordcounter.net

Many thanks to the pedagogical model developed in Mythology and Folklore and other online courses by Laura Gibbs, which have been an inspiration for this course.

Academic Calendar

College of Arts and Sciences Online



This course is currently undergoing major reconstruction to bring it into alignment with the new version of the course at Janux