by Aristotle
Further, one must observe that some causes can be expressed in universal terms, and some cannot. The primary principles of all things are the actual primary ‘this’ and another thing which exists potentially. The universal causes, then, of [20] which we spoke do not exist. For the individual is the source of the individuals. For while man is the cause of man universally, there is no universal man; but Peleus is the cause of Achilles, and your father of you, and this particular b of this particular ba, though b in general is the cause of ba taken without qualification.
Again, if the causes of substances are causes of everything, still different [25] things have different causes and elements, as was said; the causes of things that are not in the same class, e.g. of colours, sounds, substances, and quantities, are different except in an analogical sense; and those of things in the same species are different, not in species, but in the sense that the causes of different individuals are different, your matter and form and moving cause being different from mine, while in their universal formula they are the same. And if we inquire what are the [30] principles or elements of substances and relations and qualities—whether they are the same or different, clearly when the terms ‘principle’ and ‘element’ are used in several senses the principles and elements of all are the same, but when the senses are distinguished the causes are not the same but different, except that in a special sense the causes of all are the same. They are in a special sense the same, i.e. by analogy, because matter, form, privation, and the moving cause are common to all things; and the causes of substances may be treated as causes of all things in this [35] sense, that when they are removed all things are removed; further, that which is first in respect of fulfillment is the cause of all things. But in another sense there are different first causes, viz. all the contraries which are neither stated as classes nor spoken of in several ways; and, further, the matters of different things are different. [1071b1] We have stated, then, what are the principles of sensible things and how many they are, and in what sense they are the same and in what sense different.
6 · Since there were three kinds of substance, two of them natural and one unmovable, regarding the latter we must assert that it is necessary that there should be an eternal unmovable substance. For substances are the first of existing things, [5] and if they are all destructible, all things are destructible. But it is impossible that movement should either come into being or cease to be; for it must always have existed. Nor can time come into being or cease to be; for there could not be a before and an after if time did not exist. Movement also is continuous, then, in the sense in which time is; for time is either the same thing as movement or an attribute of [10] movement. And there is no continuous movement except movement in place, and of this only that which is circular is continuous.
But if there is something which is capable of moving things or acting on them, but is not actually doing so, there will not be movement; for that which has a capacity need not exercise it. Nothing, then, is gained even if we suppose eternal substances, as the believers in the Forms do, unless there is to be in them some [15] principle which can cause movement; and even this is not enough, nor is another substance besides the Forms enough; for if it does not act, there will be no movement. Further, even if it acts, this will not be enough, if its substance is potentiality; for there will not be eternal movement; for that which is potentially may possibly not be. There must, then, be such a principle, whose very substance is [20] actuality. Further, then, these substances must be without matter; for they must be eternal, at least if anything else is eternal. Therefore they must be actuality.
Yet there is a difficulty; for it is thought that everything that acts is able to act, but that not everything that is able to act acts, so that the potentiality is prior. But if this is so, nothing at all will exist; for it is possible for things to be capable of existing [25] but not yet to exist. Yet if we follow the mythologists who generate the world from night, or the natural philosophers who say that all things were together, the same impossible result ensues. For how will there be movement, if there is no actual cause? Matter will surely not move itself—the carpenter’s art must act on it; nor [30] will the menstrual fluids nor the earth set themselves in motion, but the seeds and the semen must act on them.
This is why some suppose eternal actuality—e.g. Leucippus and Plato; for they say there is always movement. But why and what this movement is they do not say, nor, if the world moves in this way or that, do they tell us the cause of its doing so. Now nothing is moved at random, but there must always be something present, e.g. [35] as a matter of fact a thing moves in one way by nature, and in another by force or through the influence of thought or something else. Further, what sort of movement is primary? This makes a vast difference. But again Plato, at least, cannot even say what it is that he sometimes supposes to be the source of movement—that which [1072a1] moves itself; for the soul is later, and simultaneous with the heavens, according to his account. To suppose potentiality prior to actuality, then, is in a sense right, and in a sense not; and we have specified these senses.
That actuality is prior is testified by Anaxagoras (for his thought is actuality) [5] and by Empedocles in his doctrine of love and strife, and by those who say that there is always movement, e.g. Leucippus.
Therefore chaos or night did not exist for any infinite time, but the same things have always existed (either passing through a cycle of changes or in some other way), since actuality is prior to potentiality. If, then, there is a constant cycle, [10] something must always remain, acting in the same way. And if there is to be generation and destruction, there must be something else which is always acting in different ways. This must, then, act in one way in virtue of itself, and in another in virtue of something else—either of a third agent, therefore, or of the first. But it must be in virtue of the first. For otherwise this again causes the motion both of the [15] third agent and of the second. Therefore it is better to say the first. For it was the cause of eternal movement; and something else is the cause of variety, and evidently both together are the cause of eternal variety. This, accordingly, is the character which the motions actually exhibit. What need then is there to seek for other principles?
7 · Since this is a possible account of the matter, and if it were not true, the [20] world would have proceeded out of night and ‘all things together’ and out of non-being, these difficulties may be taken as solved. There is, then, something which is always moved with an unceasing motion, which is motion in a circle; and this is plain not in theory only but in fact. Therefore the first heavens must be eternal. There is therefore also something which moves them. And since that which [25] is moved and moves is intermediate, there is a mover2 which moves without being moved, being eternal, substance, and actuality. And the object of desire and the object of thought move in this way; they move without being moved. The primary objects of desire and of thought are the same. For the apparent good is the object of appetite, and the real good is the primary object of wish. But desire is consequent on opinion rather than opinion on desire; for the thinking is the starting-point. And [30] thought is moved by the object of thought, and one side of the list of opposites is in itself the object of thought; and in this, substance is first, and in substance, that which is simple and exists actually. (The one and the simple are not the same; for ‘one’ means a measure, but ‘simple’ means that the thing itself has a certain [35] nature.) But the good, also, and that which is in itself desirable are on this same side of the list; and the first in any class is always best, or analogous to the best.
[1072b1] That that for the sake of which is found among the unmovables is shown by making a distinction; for that for the sake of which is both that for which and that towards which, and of these the one is unmovable and the other is not. Thus it produces motion by being loved, and it moves the other moving things. Now if something is moved it is capable of being otherwise than as it is. Therefore if the [5] actuality of the heavens is primary moti
on, then in so far as they are in motion, in this respect they are capable of being otherwise,—in place, even if not in substance. But since there is something which moves while itself unmoved, existing actually, this can in no way be otherwise than as it is. For motion in space is the first of the kinds of change, and motion in a circle the first kind of spatial motion; and this the [10] first mover produces. The first mover, then, of necessity exists; and in so far as it is necessary, it is good, and in this sense a first principle. For the necessary has all these senses—that which is necessary perforce because it is contrary to impulse, that without which the good is impossible, and that which cannot be otherwise but is absolutely necessary.
On such a principle, then, depend the heavens and the world of nature. And its life is such as the best which we enjoy, and enjoy for but a short time. For it is ever in [15] this state (which we cannot be), since its actuality is also pleasure. (And therefore waking, perception, and thinking are most pleasant, and hopes and memories are so because of their reference to these.) And thought in itself deals with that which is best in itself, and that which is thought in the fullest sense with that which is best in the fullest sense. And thought thinks itself because it shares the nature of the object [20] of thought; for it becomes an object of thought in coming into contact with and thinking its objects, so that thought and object of thought are the same. For that which is capable of receiving the object of thought, i.e. the substance, is thought. And it is active when it possesses this object. Therefore the latter rather than the former is the divine element which thought seems to contain, and the act of contemplation is what is most pleasant and best. If, then, God is always in that good state in which we sometimes are, this compels our wonder; and if in a better this [25] compels it yet more. And God is in a better state. And life also belongs to God; for the actuality of thought is life, and God is that actuality; and God’s essential actuality is life most good and eternal. We say therefore that God is a living being, eternal, most good, so that life and duration continuous and eternal belong to God; [30] for this is God.
Those who suppose, as the Pythagoreans and Speusippus do, that supreme beauty and goodness are not present in the beginning, because the beginnings both of plants and of animals are causes, but beauty and completeness are in the effects of these, are wrong in their opinion. For the seed comes from other individuals which are prior and complete, and the first thing is not seed but the complete being, [1073a1] e.g. we must say that before the seed there is a man,—not the man produced from the seed, but another from whom the seed comes.
It is clear then from what has been said that there is a substance which is eternal and unmovable and separate from sensible things. It has been shown also [5] that this substance cannot have any magnitude, but is without parts and indivisible. For it produces movement through infinite time, but nothing finite has infinite power. And, while every magnitude is either infinite or finite, it cannot, for the above reason, have finite magnitude, and it cannot have infinite magnitude because [10] there is no infinite magnitude at all. But it is also clear that it is impassive and unalterable; for all the other changes are posterior to change of place. It is clear, then, why the first mover has these attributes.
8 · We must not ignore the question whether we have to suppose one such substance or more than one, and if the latter, how many; we must also mention, [15] regarding the opinions expressed by others, that they have said nothing that can even be clearly stated about the number of the substances. For the theory of Ideas has no special discussion of the subject; for those who believe in Ideas say the Ideas [20] are numbers, and they speak of numbers now as unlimited, now as limited by the number 10; but as for the reason why there should be just so many numbers, nothing is said with any demonstrative exactness.
We however must discuss the subject, starting from the presuppositions and distinctions we have mentioned. The first principle or primary being is not movable [25] either in itself or accidentally, but produces the primary eternal and single movement. And since that which is moved must be moved by something, and the first mover must be in itself unmovable, and eternal movement must be produced by something eternal and a single movement by a single thing, and since we see that besides the simple spatial movement of the universe, which we say the first and [30] unmovable substance produces, there are other spatial movements—those of the planets—which are eternal (for the body which moves in a circle is eternal and unresting; we have proved these points in the Physics3), each of these movements also must be caused by a substance unmovable in itself and eternal. For the nature [35] of the stars is eternal, being a kind of substance, and the mover is eternal and prior to the moved, and that which is prior to a substance must be a substance. Evidently, then, there must be substances which are of the same number as the movements of the stars, and in their nature eternal, and in themselves unmovable, and without [1073b1] magnitude, for the reason before mentioned.
That the movers are substances, then, and that one of these is first and another second according to the same order as the movements of the stars, is evident. But in the number of movements we reach a problem which must be treated from the standpoint of that one of the mathematical sciences which is most akin to [5] philosophy—viz. of astronomy; for this science speculates about substance which is perceptible but eternal, but the other mathematical sciences, i.e. arithmetic and geometry, treat of no substance. That the movements are more numerous than the bodies that are moved, is evident to those who have given even moderate attention to [10] the matter; for each of the planets has more than one movement. But as to the actual number of these movements, we now—to give some notion of the subject—quote what some of the mathematicians say, that our thought may have some definite number to grasp; but, for the rest, we must partly investigate for ourselves, [15] partly learn from other investigators, and if those who study this subject form an opinion contrary to what we have now stated, we must esteem both parties indeed, but follow the more accurate.
Eudoxus supposed that the motion of the sun or of the moon involves, in either case, three spheres, of which the first is the sphere of the fixed stars, and the second [20] moves in the circle which runs along the middle of the zodiac, and the third in the circle which is inclined across the breadth of the zodiac; but the circle in which the moon moves is inclined at a greater angle than that in which the sun moves. And the motion of the planets involves, in each case, four spheres, and of these also the first and second are the same as the first two mentioned above(for the sphere of the [25] fixed stars is that which moves all the other spheres, and that which is placed beneath this and has its movement in the circle which bisects the zodiac is common to all), but the poles of the third sphere of each planet are in the circle which bisects the zodiac, and the motion of the fourth sphere is in the circle which is inclined at an angle to the equator of the third sphere; and the poles of the third spheres are [30] different for the other planets, but those of Venus and Mercury are the same.
Callippus made the position of the spheres the same as Eudoxus did, but while he assigned the same number as Eudoxus did to Jupiter and to Saturn, he thought two more spheres should be added to the sun and two to the moon, if we were to [35] explain the phenomena, and one more to each of the other planets.
But it is necessary, if all the spheres combined are to explain the phenomena, [1074a1] that for each of the planets there should be other spheres (one fewer than those hitherto assigned) which counteract those already mentioned and bring back to the same position the first sphere of the star which in each case is situated below the star in question; for only thus can all the forces at work produce the motion of the [5] planets. Since, then, the spheres by which the planets themselves are moved are eight and twenty-five, and of these only those by which the lowest-situated planet is moved need not be counteracted, the spheres which counteract those of the first two planets will be six in number, and the spheres which counteract those of the next four planets will be
sixteen, and the number of all the spheres—those which move [10] the planets and those which counteract these—will be fifty-five. And if one were not to add to the moon and to the sun the movements we mentioned, all the spheres will be forty-nine in number.4
Let this then be taken as the number of the spheres, so that the unmovable [15] substances and principles may reasonably be taken as just so many; the assertion of necessity must be left to more powerful thinkers.
If there can be no spatial movement which does not conduce to the moving of a star, and if further every being and every substance which is immune from change and in virtue of itself has attained to the best must be considered an end, there can [20] be no other being apart from these we have named, but this must be the number of the substances. For if there are others, they will cause change as being an end of movement; but there cannot be other movements besides those mentioned. And it is reasonable to infer this from a consideration of the bodies that are moved; for if everything that moves is for the sake of that which is moved, and every movement [25] belongs to something that is moved, no movement can be for the sake of itself or of another movement, but all movements must be for the sake of the stars. For if a movement is to be for the sake of a movement, this latter also will have to be for the sake of something else; so that since there cannot be an infinite regress, the end of every movement will be one of the divine bodies which move through the heaven. [30]
Evidently there is but one heaven. For if there are many heavens as there are many men, the moving principles, of which each heaven will have one, will be one in form but in number many. But all things that are many in number have matter. (For one and the same formula applies to many things, e.g. the formula of man; but [35] Socrates is one.) But the primary essence has not matter; for it is fulfillment. So the unmovable first mover is one both in formula and in number; therefore also that which is moved always and continuously is one alone; therefore there is one heaven alone.