PART FOUR
When Thomas returned to Paris for an unusual second term as regent master of theology at the Dominican convent on the Rue St Jacques, he was coming into a maelstrom. During his absence in Italy, the academic scene had changed entirely. Before, it was the animosity between the secular masters and the mendicants that had to be contended with. Now Thomas himself and his teachings were being looked at askance. And numbered among his foes were Franciscans.
The bone of contention was Aristotle. The young masters of the Faculty of Arts embraced Aristotle with an enthusiasm that led to heterodoxy. Theologians began to have second thoughts about the growing influence of the Philosopher. After all, Aristotle had taught a number of things that were in real or apparent conflict with revealed truth. Since contradictories cannot be simultaneously true, either Aristotle was wrong or Christianity was. There would of course be little doubt where a Christian’s allegiance lay – or so it seemed. But the young masters of arts who came to be called Latin Averroists sought to adopt a mind-boggling via media. They appeared to want to accept as philosophical truth what was in conflict with what they as Christians believed.
Aristotle had taught that the world is eternal. Genesis speaks of the beginning of the world’s existence. The Latin Averroists seemed to want to assent to both claims. They were called Averroists because they accepted as good money the Commentator’s reading of Aristotle. Does every person have an intellect or is there but one intellect existing apart that thinks through each of us? Averroes adopted the latter view. But it was the immaterial activity of the agent intellect that grounded Aristotle’s proof of the soul’s immortality. On Averroes’ reading, personal immortality was not only unproved, but incoherent.
The Aristotelian tenet that each substance has but one constitutive form making it to be and to be what it is was thought to run afoul of the Christian belief that for three days the dead body of Christ awaited resurrection. What made it one body? What made it Christ’s? Perhaps we need a substantial form making the body to be the body, before the advent of soul.
These and other issues, involving as they did the religious and cultural underpinnings of the university, were far more than academic questions. Shortly after Thomas’s return there was the condemnation of 1270, which expressed the concern about the inroads of pagan philosophy on the understanding of Christian doctrine. An animus against Aristotle, and philosophy itself, was growing. Thomas as we have seen, and as his contemporaries knew, had found little to balk at in the doctrine of Aristotle. His attitude was rather one of grateful amazement at the reach of the human intellect even when unaided by the ambience of grace and revelation. His position was complicated by the fact that he was every bit as appalled by the Latin Averroists as any other theologian. Waffling on the principle of contradiction seemed an odd way for alleged followers of Aristotle to behave. Thomas had to steer a middle course between the Latin Averroists on the one hand and the understandably upset theologians on the other.
He began with two polemical works, On the Eternity of the World and On the Uniqueness of Intellect. The latter is a thorough analysis and rejection of the Averroistic reading of Aristotle’s On the Soul. Correctly read, Thomas argued, Aristotle’s doctrine on soul re-enforced the Christian belief in immortality. As to the eternity of the world, Thomas attacked those who thought this was an incoherent notion. He argues that it is not. The believer must hold Aristotle mistaken in claiming the world is eternal, but he does so by appeal to Revelation. God could have created an eternal world, however, so Aristotle’s position was not incoherent nor was there any philosophical proof that it was false.
Furthermore, the commentary on Aristotle’s On the Soul which had occupied Thomas in Rome, became the first in a series of twelve commentaries, close and careful readings clearly meant to show that, correctly understood, Aristotle was one of the greatest assets of the human mind and consequently an invaluable support of Christianity. This did not mean that whatever Aristotle might have meant, we none the less can use his words, according them an irenic sense. Thomas was a serious man. It was the truth he found in Aristotle that won his allegiance in the first place. That allegiance strengthened as he subjected the text to the extended analysis that makes his commentaries a major factor in the history of Aristotelianism.
Everything I have mentioned thus far was on the margin of Thomas’s main task as regent master. The polemical writings and the Aristotelian commentaries did not emerge from his teaching. He continued his work on the Summa theologiae, he added to the fund of his Disputed Questions. But the very manner in which he did theology required the defence of Aristotle contained in polemical writings and effectively in the commentaries. In his remarkable, impressionistic book on Thomas Aquinas, G. K. Chesterton grasped the stakes involved in Thomas’s defence of Aristotle. Western civilization had reached a crossroads where obscurantism attracted some and an oddly dissociated conception of the truth of faith attracted others. Thomas was the champion of the compatibility of faith and reason and of their mutual re-enforcing, not as a slogan but as a policy pursued and illustrated in thousands of pages. His victory was not immediate – there was another condemnation in 1277 – nor was it complete. But it has stood as the fullest and most satisfying synthesis of faith and reason produced in the Christian era.
The goal of philosophy is such knowledge as men can attain of the divine, but there is a sense in which God and other separated substances are as far from the connatural object of our mind as can be. Philosophy begins with the study of the things known to us through sense experience. Only on the basis of a science of nature are we in a position to see physical objects as effects of a cause which is utterly different from them.
In Chapter 2 we read a youthful work of Thomas in which he summarized the main points of Aristotle’s teaching about physical objects. However impressive, and useful, that opusculum might be, it does not adequately convey how these doctrines are forced upon the inquiring mind. But it is not typical of Thomas’s invocation of the Aristotelian tenet that the things that come to be as the result of a change are composites of matter and form. When late in his life he got around to commenting on the Physics and other natural writings of Aristotle, Thomas was able to speak at length of the trajectory of our knowledge of the natural world.
The fundamental Aristotelian text is Book I of the Physics. A close reading of the text shows the progression within the analysis of change – from incidental change to substantial change – as well as the role that art, particularly medicine, plays in Aristotle’s analysis of the natural world.
A fundamental methodological insight of Aristotle’s is that our knowledge progresses from confusion to distinction, from generalities to specific descriptions. This methodological truth is seen to be the basis for relating the many natural writings of Aristotle. At the outset of his commentary on On the Heavens, Thomas sketches the trajectory of natural philosophy and in a prologue to On Sense and the Sensed Object, he completes the map with the inclusion of the life world.
COMMENTARY ON THE PHYSICS I.I
When the objects of an inquiry, in any department, have principles, causes, or elements, it is through acquaintance with these that knowledge, that is to say scientific knowledge, is attained. For we do not think that we know a thing until we are acquainted with its primary causes or first principles, and have carried our analysis as far as its simplest elements. Plainly therefore in the science of nature, as in other branches of study, our first task will be to try to determine what relates to its principles.
The natural way of doing this is to start from things which are more knowable and obvious to us and proceed towards those which are clearer and more knowable by nature; for the same things are not ‘knowable relatively to us’ and ‘knowable’ without qualification. So in the present inquiry we must follow this method and advance from that which is more obscure by nature, but clearer to us, towards what is more clear and more knowable by nature.
Now what is to us plain and obvious at first is rather confused masses, the elements and principles of which become known to us later by analysis. Thus we must advance from generalities to particulars; for it is a whole that is best known to sense perception, and a generality is a kind of whole, comprehending many things within it, like parts. Much the same thing happens in the relation of the name to the formula. A name, for example ‘round’, means vaguely a sort of whole; its definition analyses this into its particular senses. Similarly a child begins by calling all men father and all women mother, but later on distinguishes each of them.
Aristotle, Physics 1.1
1. We intend to comment on the Physics, which is the first book of natural science. That is why it was necessary as it begins to assign what the matter and subject of natural science might be. It should be known that since all knowledge is in the intellect, something becomes actually intelligible insofar as it is in some way abstracted from matter. Insofar as things are differently related to matter they pertain to different sciences. And since every science is acquired by means of demonstration, and the middle term of the demonstration is a definition, it is necessary that sciences be distinguished by different modes of definition.
2. It should be known, therefore, that there are some things whose existence depends upon matter nor can they be defined without matter. There are other things which, although they cannot exist except in sensible matter, sensible matter does not enter into their definitions. These two kinds of thing differ as curve and snub do. For the snub is in sensible matter, and it is necessary to put sensible matter into its definition, for it is a curved nose; all natural things are like that, such as man and stone. The curve, however, although it can only exist in sensible matter, sensible matter is not put into its definition; all mathematicals are like this, such as numbers, magnitudes, figures. There are some things which depend on matter neither in order to exist nor to be defined, either because they never exist in matter, like God and the other separated substances, or because they are not always in matter, such as substance, potency and act, and being itself.
3. Metaphysics is concerned with this last sort; mathematics is concerned with things which, while they depend on matter in order to exist, do not have matter in their definitions. Natural science, or physics, studies things which depend on matter not only in order to exist, but also with respect to their definitions. Because everything that has matter is mobile, mobile being is the subject of natural philosophy. Natural science is concerned with natural things and nature is a principle of motion and rest in that in which it is; therefore, natural science is concerned with things which have in them a principle of motion.
4. First and foremost we must study what is common, lest it become necessary to repeat it again and again in treating the parts of it. Thus it was necessary to put first in natural science a book in which would be studied what belongs to mobile being in general, just as first philosophy in which is treated what is common to being as being comes before all other sciences. This book of the Physics is also called Hearing of the Natural, because it was taught to listeners by way of teaching. It subject is mobile being as such. I do not say mobile body, because that every mobile thing is a body is proved in this work, and no science proves its own subject. Therefore at the outset of On the Heavens, which follows on this, he begins to make body known. There follow on this book other works of natural science in which the species of mobile beings are treated, as in On the Heavens, of being mobile according to local motion, which is the first species of motion; in On Generation, of motion towards form and of the first mobiles, that is, the elements, with respect to their changes in general; their specific changes are treated in the Meteorology; mixed inanimate mobile things are treated in Of Minerals; and animate things in On the Soul and the books that follow on it.
5. The Philosopher begins with a preface in which he shows the order of proceeding in natural science. He does two things: first, he shows that we must begin with a consideration of principles; second, that among principles, we must begin with the most universal, ‘The natural way of doing this…’ He gives the following argument on behalf of the first point. In all sciences where there are principles and causes and elements, understanding and knowledge proceed from knowledge of the principles, causes and elements. But the science of nature has principles, elements and causes. Therefore, in it we must begin with a determination of the principles. When he says ‘understanding’ this refers to definitions, and ‘knowledge’ refers to demonstration. For both demonstrations and definitions are taken from causes since a complete definition is a demonstration in everything but arrangement, as is said in the Posterior Analytics. He does not mean the same thing by principles, causes and elements, for the element is that from which a thing is first composed and which remains within it, as is said in Metaphysics 5, as letters are elements of speech, but not syllables. Causes are that on which things depend to be or to become, hence even what is outside a thing or what is in it but is not an element can be called causes. Principle implies the order of some process, so something can be a principle which is not a cause; as that from which motion begins is a principle though not a cause, and the point is the principle of the line but not its cause. Thus by principles he seems to mean moving and agent causes, in which especially the order of any process in found; by causes he seems to mean formal and final causes, on which a thing depends especially with respect to being and becoming; by elements, properly the first material causes. He uses these names disjunctively, not conjunctively, in order to indicate that not every science demonstrates through all the causes. For mathematics demonstrates through formal cause alone, metaphysics chiefly by formal and final cause, but also the agent cause; but natural science demonstrates through all the causes.
He proves the first proposition of his argument from common opinion, just as in the Posterior Analytics. Because someone thinks himself to know something, when he knows all its causes from first to last. Nor do we need to take causes and elements and principles differently than above, as the Commentator wishes, but in the same way. He says even to the elements because that which is ultimate in knowledge is matter. Matter is for the sake of form, and form is from the agent for the sake of an end, if it is not itself the end; for example, we say that the saw has teeth in order to cut, and must be iron in order to be apt for cutting.
6. When he says, ‘The natural way…’ he shows that among principles we must first determine the most universal. And first he shows this by an argument, secondly through a sign, ‘Now what is plain and obvious…’ Here is the argument. It is natural to us to proceed in knowing from things which are more known to us to those which are more known in nature. But the things which are more known to us are confused, as universals are. Therefore, we must proceed from universals to singulars.
7. As clarification of the first proposition, he suggests that what is more known to us and what is more known according to nature are not the same. Because the natural mode or order of learning is to go from what we know to what we do not, we must go from what is more known to us to what is naturally more known, which has more being. A thing is knowable insofar as it is being. A thing is more of a being insofar as it is more actual. Hence the most actual things are what are more known in their natures. But for us the opposite is true, insofar as we proceed in understanding from potentiality to act, and the beginning of our knowledge is from sensible things, which are material, and only potentially intelligible. It is such things that are more known to us than separated substances, which are more known according to nature, as is evident in Metaphysics 2. He does not say more known in nature, as if nature knew them, but because they are more known in themselves and according to their own nature. He says more known rather than more certain, because in the sciences it is not just any kind of knowledge that is sought, but the certitude of knowledge.
To understand the second proposition, we must know that confused means here that which contains things in itself potentially and indistinctly. And because to know something indistinctly is midway between pure potentiality and perfect act, since our intellect proceeds from potency to act, it is the confused rather than the distinct that first occurs to it, and science is actually complete when it arrives by analysis at distinct knowledge of principles and elements. This is the reason why the confused rather than the distinct is first known by us. That universals are confused is obvious, because universals contain in themselves their species potentially, and he who knows something in general, knows it indistinctly; and his knowledge will be distinct when each of the things potentially contained in the universal is actually known. For he who knows animal, knows rational only potentially. We first know something potentially and then actually. Therefore, we proceed according to this order of learning from potency to act, and we know animal before we know man.
8. This seems to be contrary to what the Philosopher says in Posterior Analytics 1, namely that singulars are more known to us, but universals are more known simply speaking or according to nature. But it should be understood that there he takes singulars to be individual sensible things, which are more known to us because sense knowledge, which is of singulars, in us precedes intellectual knowledge, which is of universals. Because intellectual knowledge is more perfect, since universals are actually intelligible and singulars, when they are material, are not, simply and according to their nature universals are more known. Here, however, he means by singulars not individuals, but species which are more known in nature, as being more perfect and yielding more distinct knowledge; genera are more known to us as yielding potential and confused knowledge. The Commentator, it should be known, explains it otherwise.
He comments that when he says, ‘The natural way…’, the Philosopher wants to show the mode of demonstration in this science, because he demonstrates through effects and what is posterior in nature, and thus what he says is to be understood of the process of demonstrating and not of determining. And when he says, ‘Now what is plain to us…’ he intends to show, according to the Commentator, what are more known for us and less known in nature, namely, things composed of simples, understanding composed as confused. Finally he concludes that we should proceed from the more to the less universal as a kind of corollary.
His explanation is clearly wrong because it does not bring it all together into one intention. The Philosopher has no intention here of showing the mode of demonstration of this science, since he does this in the second book following the order of determining. What is more, confused ought not to be explained as composite, but as indistinct. Nor would he be able to deduce anything from universals, since genera are not composed of their species.
9. When he says, ‘For it is a whole that is best known…’ he manifests what he has proposed by three signs, the first of which is taken from the sensible integral whole. And he says that the sensible whole is more known to sense; therefore the intelligible whole is more known to intellect. The universal is a kind of intelligible whole which comprises many parts, namely, its inferiors. Therefore the universal is more known to intellect so far as we are concerned. This proof seems ineffective, because he uses whole and part and comprehension equivocally. It should be said that the integral and universal wholes agree in this that both are confused and indistinct. For just as one who apprehends a genus does not apprehend its species distinctly but only potentially, so one who sees a house does not yet distinguish its parts. Since it is by reason of confusion that the whole is known by us before its parts, the same reason applies to both wholes. To be composed is not common to both wholes, so it is clear that he significantly says confused and not composed.
10. When he says, ‘Much the same thing…’ he gives another sign from the intelligible integral whole. The defined is to the parts of the definition somewhat as an integral whole, insofar as the defining parts are actually in the defined. But one who hears a name, say, man or circle, does not immediately distinguish the defining principles, so the name is a kind or whole and indistinct, but the definition divides into singulars, that is, states distinctly the defining principles. But this seems contrary to what he said above, for the defining principles seem to be more universal, which he said to be more known to us. Again, if the defined were more known to us than the defining principles, the defined would not be made known to us by the definition. It should be said that the defining principles in themselves are more known to us than the defined, but the defined is known to us before we know that these are its defining principles. As we know animal and rational before man, but man is first known to us confusedly, then that animal and rational are his defining principles.
11. Then when he says, ‘Similarly a child…’ he gives a third sign taken from the more universal sensible. For just as the more universal intelligible is first known by us with respect to intellect, as for example animal prior to man, so the more common sensible is first known to us according to sensing, for example this animal before this man. And I say prior to sense both according to place and time. According to place, because when someone is seen at a distance, we first perceive him to be a body and then to be an animal, and that we perceive before perceiving that he is a man, and then that he is this man who is Plato, who is his father. And so he says that a child first calls all men fathers and all women mothers, but later knows each one determinately. This clearly shows that we first know something confusedly rather than distinctly.
PREFACE TO THE COMMENTARY ON ON THE HEAVENS
1. As the Philosopher says in Physics 1.1, ‘When the objects of an inquiry, in any department, have principles, causes or elements, it is through acquaintance with these that knowledge, that is to say, scientific knowledge, is attained.’ In these words the Philosopher clearly shows that there is an ordered process in sciences, insofar as we proceed from first causes and principles to proximate causes, which are the elements making up the essence of a thing. This is reasonable, for the procedure in science is a work of reason, whose proper work is ordering. Hence, in every work of reason an order can be seen, insofar as it proceeds from one thing to the next. This is clear both in practical reason, whose concern is the things that we do, and in speculative reason, which considers things made by another.
2. In the consideration of practical reason one finds a process from the prior to the posterior on the basis of a fourfold order: (1) according to the order of apprehension, insofar as the artisan first grasps the form of the house absolutely, and then produces it in matter; (2) according to the order of intention, insofar as the artisan intends to complete the whole house, and for the sake of that does whatever he does as to the parts of the house; (3) according to the order of composition, insofar as he first dresses stones and afterwards lays them to make a wall; (4) according to the order of maintenance of the work, insofar as the artisan first lays the foundation, on which the other parts of the house are sustained.
Similarly, there is found a fourfold order in the considerations of speculative reason. (1) Insofar as it proceeds from the common to the less common. This answers analogously to the first order, which we called of apprehension: for universals are considered according to absolute form, particulars are considered insofar as that form is applied to matter, as the Philosopher says: ‘There is a difference, then, between “this universe” and simply “universe”; the second is form and shape, the first form in combination with matter; and any shape or form has, or may have, more than one particular instance.’ (2) The second order is that found when we proceed from whole to parts, and this answers analogously to the order we called of intention, insofar as the whole is considered prior to the parts, not just any, but the material parts and those of the individual. For example, the semicircle, into whose definition circle is put (the semicircle is half a circle), and the acute angle, into whose definition the right angle is put (the acute angle is less than the right angle). It is incidental to circle and to right angle that they be divided like this, hence these are not parts of the species [of the definitions of circle and right angle]. Parts of the species are prior in consideration to the whole, and are put into the definition of the whole, as flesh and bones are put in the definition of man, as is said in Metaphysics 7.10. (3) The third order is seen when we proceed from simples to composites, insofar as the composites are known by means of the simples, as by their principles. This order is compared to the one that was called of composition. (4) The fourth order arises because it is necessary to consider the principal parts first, such as heart before arteries and blood. And this is analogous to the practical order, insofar as the foundation must first be laid.
3. This fourfold order is also considered in the procedure of natural science. For first are determined what is common to nature, in the books of the Physics in which the mobile is treated insofar as it is mobile. It remains for the subsequent books of natural science to apply these common features to their proper subjects. The subject of motion is magnitude and body, since nothing is moved unless it is quantified. In bodies three other orders are to be noticed: one, insofar as the whole corporeal universe is prior in consideration to its parts; another, insofar as simple bodies are considered before mixed bodies; a third, insofar as among simple bodies it is necessary first to consider the first, that is, the heavenly body, by which all the others are stabilized. These three are considered in this book, which some Greeks called On the Heaven. Things pertaining to the whole universe are treated here, as is clear from the first book; things pertaining to the celestial bodies, as is clear from the second book; things pertaining to the other simple bodies, as is clear from the third and fourth books. This book is reasonably put first after the Physics, therefore. On this account immediately at the beginning of the book he treats of body, to which must be applied all the things which were said of motion in the Physics.
4. Because this book treats of different things, there was a doubt among the ancient commentators of Aristotle about its subject. Alexander thought that the subject principally treated in this book was the universe itself. Hence, since heaven is said in three ways, sometimes meaning the ultimate sphere, sometimes the whole body which moves in a circle, sometimes the universe itself, he asserts that this book has the title Of the Heaven, as if it is ‘Of the Universe’ or ‘Of the World’. In this assertion he assumes that the Philosopher discusses things pertaining to the whole universe in this book, such as that it is finite, that it is only one, and other similar things.
On the contrary, it seemed to others that the subject principally treated in this book is the celestial body that moves in a circle, and for this reason it is titled On the Heaven. Other bodies are discussed in the book either by way of consequence, insofar as they are contained by the heaven and receive its influence, as Iamblichus said, or incidentally, insofar as knowledge of the other bodies is assumed to manifest what is said of the heaven, as Syrianus said.
But this seems improbable because after the Philosopher treats of the heaven in the second book, in the third and fourth he adds the consideration of all simple bodies, as if principally interested in them. It is not the Philosopher’s practice to assign the principal part of a science to things taken up incidentally.
Therefore it seemed to others, as Simplicius said, that the intention of the Philosopher in this book is to study simple bodies, insofar as they share in the common meaning of simple body. It is because the heaven is the chief among simple bodies, on which others depend, that the whole book is called On the Heaven. And, as he says, it precludes that things which pertain to the whole universe might be determined in this book, because such conditions belong to the universe insofar as they belong to heavenly body, namely, to be finite, sempiternal and the like. If the chief intention of the Philosopher were to determine what the universe or world is, Aristotle would have had to extend the consideration to all the parts of the world, down to plants and animals, like Plato in the Timaeus.
But for the same reason we can argue against Simplicius because if in this book he intended to treat principally simple bodies, everything pertaining to simple bodies would have to be treated in it, but what it actually treats are the things which pertain to their lightness or heaviness; the others are discussed in On Generation.
5. Therefore the opinion of Alexander seems more reasonable: the subject of this book is the universe itself, which is called ‘heaven’ or ‘world’; and he treats simple bodies in this book insofar as they are parts of the universe. The corporeal universe is constituted of its parts according to the order of position. Therefore in this book he treats only those parts of the universe which first and as such have position in the universe, namely, simple bodies. That is why he does not discuss the four elements in this book insofar as they are warm or cold, or anything like that, but only with reference to heaviness and lightness, by which their place in the universe is determined. The place of other parts of the universe, such as rocks, plants and animals, is not determined according to themselves, but according to simple bodies, and that is why they are not discussed in this book. This is consonant with what it is customary among the Latins to say, that this book treats of body mobile as to position, or according to place, which indeed is a motion common to all the parts of the universe.
PREFACE TO THE COMMENTARY ON ON SENSE AND THE SENSED OBJECT
Having now considered the soul, by itself, and its several faculties, we must next make a survey of animals and all living things, in order to ascertain what functions are peculiar, and what functions are common, to them. What has already been determined respecting the soul must be assumed throughout. The remaining parts of our subject must now be dealt with, and we may begin with those that come first.
The most important attributes of animals, whether common to all or peculiar to some, are, manifestly, attributes of soul and body in conjunction, for example sensation, memory, passion, appetite and desire in general, and, in addition, pleasure and pain. For these may, in fact, be said to belong to all animals. But there are, besides these, certain other attributes, of which some are common to living things, while others are peculiar to certain species of animals. The most important of these may be summed up in four pairs, viz. waking and sleeping, youth and old age, inhalation and exhalation, life and death. We must examine these, determining their respective natures, and the causes of their occurrence.
But it behoves the natural scientist to obtain also a clear view of the first principles of health and disease, inasmuch as neither health nor disease can exist in lifeless things. Indeed, we may say of most physical inquirers, and of those physicians who study their art more philosophically, that while the former complete their works with a disquisition on medicine, the latter start from a consideration of nature.
That all the attributes above enumerated belong to soul and body in conjunction is obvious; for they all either imply sensation as a concomitant, or have it as their medium. Some are either affections or states of sensation, others, means of defending and safe-guarding it, while others, again, involve its destruction or privation. Now it is clear, alike by reasoning and without reasoning, that sensation is generated in the soul through the medium of the body.
Aristotle, On Sense and the Sensed Object
1. As the Philosopher says in On the Soul 3, as things are separable from matter so do they relate to intellect. For a thing is intelligible to the degree that it is separable from matter. Hence things which are of their nature separate from matter are in themselves actually intelligible; but things which are abstracted by us from their material conditions become actually intelligible by the light of our agent intellect. And, because the habits of a power are specifically distinguished according to the differences in the object of the power, the habits of the sciences, by which intellect is perfected, are also distinguished according to different separation from matter. That is why the Philosopher in Metaphysics 6 distinguishes the kinds of science according to the different mode of separation from matter. For things which are separate from matter as they exist and as they are defined pertain to metaphysics; things which are separate in definition but not as they exist pertain to mathematics; things which include sensible matter in their definitions pertain to natural science.
2. Just as the different kinds of science are distinguished insofar as things are differently separable from matter, so in each of the sciences, and especially in natural science, the parts of the science are distinguished according to the different mode of separation and concretion. Because universals are more separated from matter, in natural science we advance from the more to the less universal, as the Philosopher teaches at the outset of the Physics. Hence he begins natural science with a treatment of what is most common to all natural things, namely motion and the principle of motion. And finally he advances by way of concretion or application of the common principles to certain definite mobile things, some of which are living bodies, with which he proceeds in a similar manner, dividing the consideration into three parts. First, he considers the soul in itself, as it were by a kind of abstraction. Second, he considers what pertains to the soul according to a kind of concretion or application to body, but in general. Third, he introduces an inquiry which applies all these to the single species of animals and plants, determining what is proper to each species. The first inquiry is found in On the Soul. The third in the books On Animals and On Plants. The middle inquiry is contained in books which he wrote about things which pertain commonly, either to all animals or to many kinds of them, or even to all living things, which is the intention of this work.
3. It should be considered that in On the Soul 2 four grades of living things were described, the first of which were those which have only the nutritive part of the soul by which they live, such as plants. But some are such that they have also sense but without progressive motion, such as the imperfect animals, like oysters. Some also have progressive local motion, such as the perfect animals, for example the horse and cow. Some have intellect over and above all these, such as men. The appetitive, although it is a fifth kind of power of the soul, does not constitute a fifth grade of living things, because it always follows sense.
4. Of these, intellect is not the act of any part of the body, as is proved in On the Soul 3, hence it cannot be considered by way of concretion or application to body or to any bodily organ. Its greatest concretion is in the soul, and its highest abstraction in the separated substances, so Aristotle did not write a book on intellect and the object of intellect after On the Soul. If he had written it, it would not have pertained to natural science but to metaphysics which considers separated substances. All the others are acts of some part of the body and therefore there can be a special consideration of them by application to the body or to bodily organs beyond the consideration they received in On the Soul.
5. This mid-consideration should be divided into three parts, of which one contains the things which pertain to the living as living, and this in the book On Death and Life, in which he discusses inhaling and exhaling by which things are preserved in life, youth and age, by which the states of life are distinguished. So too in the book called On Length and Brevity of Life and in the book On Health and Sickness, which pertain to the disposition of life, and in the book On Food and the Edible, one we do not have in Latin. Others pertain to the mover, in two works, The Cause of Movement in Animals and On the Progress of Animals, in which he treats of the parts of animals adapted to movement. The third pertains to the sensitive part, in which what pertains to the acts of the interior and exterior senses can be considered. In this regard, the consideration of the sensitive is contained in this book which is called On Sense and the Sensed Object, that is, of the sensitive and the sensible, and the book contains the treatise On Memory and Reminiscence. And to the consideration of the sensitive also pertains what makes a difference in the sense in sensing, which is treated in the book On Sleeping and Waking.
6. Because one must pass from the more similar to the dissimilar, such seems reasonably to be the order of these books such that after On the Soul, in which the soul as such is treated, there immediately follows this book On Sense and the Sensed Object, because sensing pertains to soul more than to body, after which should be placed the book On Sleep and Waking, which implies the tightening and loosening of sense; then follow the books which pertain to the moving principle, which is closer to sense. In the last place are put the books which pertain to the common consideration of the living, because this largely concerns the disposition of the body.
7. This book, then, which is called On Sense and the Sensed Object, is divided into two parts: a preface and the treatise. With respect to the first, he does two things, first states his intention, showing what has to be treated, and second gives the reason why it is necessary to treat of them, ‘The most important attributes.’ First, he says that of soul itself it has already been determined in On the Soul, where he defined soul. Next it must be determined concerning each act and power of it, but I say this on its part. For since powers of the soul, other than intellect, are acts of some parts of the body, they can be considered in two ways. In one way, insofar as they pertain to soul, as its powers and faculties, in another way, on the part of the body. In On the Soul, the powers of the soul were determined on the part of the soul itself, but now we must consider animals and all things having life: which he adds for the sake of determining concerning plants, which operations are proper to each single species of animal and plant, and which are common, as belonging to all living things or to all animals or to many kinds of them, what has been said of soul underlies or is presupposed, that is, we use them in the following as suppositions already made manifest. Of the rest we say, and first the first, that is, first the common and then the proper. For this is the fitting order of natural science, as determined at the outset of the Physics.
8. Then when he says, ‘The most important attributes…’ he shows the need for the present consideration, for if both the common and proper activities of animals and plants were proper to the soul itself, the consideration in On the Soul would suffice. But because they are common to soul and body there must be after the consideration of soul a consideration of such things in order to know what kind of dispositions are required in bodies for operations and passions of this kind. Therefore the Philosopher here shows all the things common to soul and body, concerning which he does three things. First, he states his intention; second, he enumerates the things he intends to discuss – ‘for example sensation, memory, passion…’ Third, he proves what he has proposed: ‘That all the attributes above enumerated…’ First, then he says that among the things that pertain to animals and plants, those especially and chiefly are common to all animals or to many or are proper to particular species, and even at first glance seem to be common to soul and body. So a consideration beyond that of soul itself is required.
9. Then when he says, ‘for example sensation, memory, passion, etc’ he enumerates what falls to his intention. First, he states things pertaining to the sensitive part, namely sense and memory, making no mention of others, such as imagination and the estimative power, because they are not distinguished from sense on the basis of the thing known: they are of things present or quasi-present, but memory is distinct because it is of the past as past.
10. He sets down what pertains to the moving principle. Sensitive appetite is the proximate principle of motion in animals, and is divided into two powers, namely the irascible and concupiscible, as is said in On the Soul 3. So he mentions wrath as pertaining to the irascible power and desire as pertaining to the concupiscible, from which two passions as from the most manifest the two powers mentioned are named. For the concupiscible is denominated from desire, the irascible from wrath. But because there are other passions pertaining to the appetitive power, he adds, ‘and desire in general’, as it comprises whatever pertains to the appetitive power.
11. Joy or sadness follow on all the passions of the soul, whether of the irascible or concupiscible, as is said in Ethics 2, ‘in addition, pleasure and pain’, as encompassing passions. And he adds that what has been enumerated are found in nearly all kinds of animals, ‘nearly’ because many of these are found in both perfect and imperfect animals, namely sense, desire, appetite, joy and sorrow. Imperfect animals have only the sense of touch but they have imagination, desire, joy and sorrow, although indeterminately, and they are indeterminately moved, as is said in On the Soul 2. Memory and anger are wholly absent from them, but exist only in perfect animals. The reason is that not everything of a lower kind, but only the highest and most perfect, attains to a participation in a likeness of that which is proper to a higher kind. Sense differs from intellect and reason, because the latter are of universals, which are everywhere and always, but sense is of singulars, which are here and now. In its proper nature, therefore, sense is cognoscent only of present things.
12. If there is a power of the sensitive part which extends to other than present things, this is due to a proportional participation in reason or intellect. Thus memory, which is cognoscent of past things, is found only in perfect animals, as something supreme in sense cognition. Similarly sense appetite which properly follows on sense has as its object what is pleasurable to sense, which pertains to the concupiscible power common to animals. But that an animal tends to something arduous, such as a fight or the like, has a similarity to rational appetite which seeks something for the sake of an end which is not pleasant to the senses. Therefore anger, which is a desire for revenge, pertains only to perfect animals because of their propinquity to the genus of rational things.
13. Next he states things which pertain somewhat to the notion of life. And he says that along with the foregoing other things are found in animals, some of which are common to whatever shares life, not only animals, but also plants. Some pertain only to some kinds of animal and the chief of these are listed in a fourfold conjunction: sleep and waking, which are found in all animals but not in plants; youth and old age, which are found in both animals and plants; inhalation and exhalation, which are found in some kinds of animal, namely those with lungs; life and death, which are found in all living things in this lower world. He says that we must ask of each of these what it is and what its cause is. And because he called them the most important, he adds that there are some of less importance, like health and disease, which are not found in individuals of all these kinds in which they might be. This is not true of the most important, which are natural to all living things, both animals and plants.
14. He says that it is also a task of natural philosophy to discover the first and universal principles of health and disease; it is for the physician to consider their particular principles; he is the artisan who causes health and like any art his must concern itself with the singulars that come under this project, since operations bear on singulars. That this is a task of natural philosophy he proves when he says, ‘But it behoves the natural scientist…’ And this in two ways.
15. First by argument. Health can only be found in living things, from which it is clear that the living body is the proper subject of health and disease. But the principles of a subject are the principles of its proper accident. Hence, since it pertains to natural philosophy to consider the living body and its principles, it must also consider the principles of health and disease.
16. Second, he proves it by a sign or example, which he concludes from the argument just given. For many natural philosophers complete their inquiry with things that belong to medicine, and many physicians, who pursue the art of medicine philosophically, using not only experience but seeking causes, begin the medical inquiry where natural philosophy leaves off. From which it is clear that the study of health and disease is common to philosopher and physician. But since art is not the chief cause of health, but aids nature and assists it, it is necessary that the physician take from natural philosophy the more important principles of his science, as the navigator borrows from the astronomer. This is why physicians practising medicine well begin from natural science. But if there are artefacts which come about only by art, like the house and ship, these in no way belong to natural philosophy any more than things which come about only by nature pertain to the consideration of art, except insofar as art uses natural things.
17. When he says, ‘That all the attributes…’ he proves his thesis, namely that all the foregoing are common to soul and body, and fashions this argument: All the foregoing pertain to sense; but sensing is common to soul and body, for it belongs to soul through the body; therefore all the foregoing are common to soul and body. He manifests the first premiss by induction from what has been said, for some come about with sensation, namely what pertains to sense cognition, like sense, imagination and memory; some come about through the sensation, such as those that pertain to the appetitive power which are moved by the apprehension of the senses. Of the others, which more manifestly pertain to body, some are states of sensation, like sleep, which is a binding of the sensation, and wakefulness, which loosens it; some are relations of sensation, namely youth and old age, which arise from the fact that sensation is as it should be or is weak; some preserve and guard sensation, such as respiration, life and health; some are destructive of it, like death and infirmity.
The second premiss, namely that sensation is common to soul and body, is manifest, he says, with or without argument. The argument is obvious: because sense is affected by the sensible, as was shown in On the Soul, and sensibles are material and corporeal, it is necessary that that which is affected by the sensible be corporeal. It is manifest without argument by experience that a disturbance of the sense organs impedes the activity of sensation, and if they be destroyed, sense is completely taken away.