International Catholic University


Philosophy of Nature

2nd Lecture: Nature -- The Inner Dimension

In our first lecture we sketched some fundamental concepts that are necessary for beginning the philosophy of nature. Our focus was on the theory of knowledge -- how sense knowledge differs from intellectual knowledge, how we form universals through a process of concept formation, and then the various types of concepts we attain through different degrees of abstraction. We explained that the philosophy of nature considers concepts that always involve some relationship to sensible matter, and that in this respect its concepts differ from those studied in mathematics and metaphysics.

We also explained the difference between the real concepts studied in natural science, mathematics, and metaphysics, and the type of concept studied by the logician. We referred to these as logical concepts, or concepts of concepts. Our detour through logic enabled us to explain what is meant by the predicables and the categories, giving brief definitions of each. We also talked briefly about how a proposition is formed by joining concepts as a subject and a predicate, in the form "S is P."

Finally we explained the concept of science as this was understood by Aristotle and how it appears in diminished and less rigorous form in modern science. Scientific knowledge for Aristotle is certain knowledge through causes. The science of nature, for him, poses a special difficulty because nature's causes are generally hidden from us, whereas its effects are apparent to us through sense knowledge. So, in the science of nature, we must begin with what is more known to us, the sense knowledge of effects, and proceed from this to what is more known to nature or in itself, by an intellectual grasp of their causes.

1. The Concept of Nature

The title of this lecture is "Nature -- The Inner Dimension." This is the same as the title of the first chapter in The Modeling of Nature, where the topic is more fully explained. What we will be considering here is really the subject of natural science or philosophy of nature, namely, nature itself. We add to this the expression "the inner dimension," to convey some of the difficulty of grasping precisely what nature is. A thing's nature is not something readily apparent on the thing's surface. A special intellectual effort is required to grasp the concept of nature and to understand it in its full meaning.

A first approach to the concept is to see the world of nature as what is experienced when one goes into a primeval forest or gazes on a starry night into the depths of space. The natural is then perceived as opposed to the artificial. It is what is free from human effort, what comes into being and runs its course without benefit of man's assistance or influence.

Another sense of the natural differentiates it from the forced or the violent. The forced and the violent are done from without or by coercion. The natural comes from within the subject being studied. In this way of speaking, things have natures that are the sources of the activities they originate and so are peculiarly their own.

Putting the two senses together, we may describe the world of nature as what is capable of coming into existence apart from human influence and as made up of things that have within themselves natures or internal sources of their distinctive activities. Examples of things with natures are minerals, plants, and animals, chemical elements and their compounds, planets, stars, and galaxies. All of these come into being and pass away, they are all changeable in one way or another. Yet they enjoy periods of relative stability during which they respond to, or interact with, objects around them.

To say of something that it is lead, or a geranium, or a horse, is to specify its nature. We humans have the capacity to grasp a thing's nature from its appearance and from the way it acts and reacts in various circumstances. To say of a horse that it is "a large mammal with solid hoofs that lives off plants" is to define its nature. It actually tells us the meaning of the word "horse" and how we can differentiate horses from other objects. And grasping that meaning is the work of the intellect, not merely the work of the senses. Natures are universals, objects of the intellect, as we explained in our last lecture.

To sum up: the nature of a thing is an inner dimension that makes the thing be what it is, that serves to differentiates it from other things, and that accounts for its distinctive activities and responses. We first grasp natures in a general way as we learn a language and attach meanings to words we use. We then develop and refine our understanding as we gain more information and experience about the objects we know. A horse trainer or a veterinarian obviously knows more about horses than does a youth who has little contact with them. Yet even the child who is able to say "That is a horse" grasps the same nature than does the expert, while doing so in a general and less specific way.

2. The Causal Model

The fact that a nature is only gradually disclosed in experience, and rarely is exhaustively understood, makes it especially suitable for study through modeling techniques. For our purposes a model is an analogue or analogy that promotes the gradual understanding of something that is not apparent in sense experience. When we encounter something new, we attempt to understand it by noting its similarities and differences with things that are familiar to us. A model enables us to do that. It enables us to use things we know, or at least think we know, to advance into the realm of the unknown.

The first model we introduce is a simple explanatory model known as the causal model. This takes its origin from the world of artifacts and is easily applied to the world of nature. It identifies four factors that are called causes, though not all in the same sense, since each functions in a distinctive way in a causal explanation. These four factors are usually identified as matter, form, agent, and end. More explicitly, matter becomes material cause, form formal cause, agent efficient cause, and end final cause.

When analyzing a chair on the basis of this model, we have no difficulty identifying the first two factors, matter and form. The matter is the stuff or material out of which the chair is made and which remains in it. An example would be wood, or, to be more precise, cherry or oak. The form is the shape or design imposed on the wood during the chair's making. Both of these factors are internal to the chair, they are within it and explain why it is what it is. On this basis we call matter and form internal causes.

The remaining two factors, agent and end, are external to the chair and serve to explain how the chair came to be. The agent is the craftsman who fashioned it from raw materials. The end is the goal or objective the craftsman had in mind when doing so -- say, to make a piece of furniture on which one can sit comfortably. Both of these explain the making of the chair. They are not in the chair in the same way as matter and form, and so they are called external causes. But once made, the chair retains a relationship to its maker. It also embodies the goal that motivated its making. And if it does that completely, it is said to be a good chair.

I am using graphical aids throughout these lectures that are available to those taking the course for credit. Many are these are diagrams found in my The Modeling of Nature, published by The Catholic University of America Press, in 1996. Fig. 2.1 (on p. 24 of Modeling) provides a graphic illustration of this causal model. It makes use of a circle and three regular polygons to show how the four causes are distinguished and to detail the interrelationships between them. The agent (A) is shown as a triangle. It acts on the matter (M), represented as a square. Its action brings forth the form (F), which is diagramed as a circle. And the production of the form is itself the end (E) of the making process, which is shown as a hexagon. Thus all four causes are separate but interconnected: the agent (A) acting on the matter (M) and educing from it the form (F) as the end (E) of the process.

In the artificial analogue this fourfold structure of causality is rather easily seen. An agent or efficient cause (the craftsman and the tools used) worked on a particular kind of matter (say, oak) and shaped it into a form (that of a kitchen chair) that had a distinctive end (providing something comfortable to sit on, say, while eating).

Our problem now is to see how these same four causes can be uncovered in the order of nature and how, when uncovered, they provide us with an insight into the inner dimension of natural entities. By natural entities I mean substances that have natures that serve to explain their distinctive activities -- natural substances such as elements and compounds, plants, animals, stars, and planets. We must examine the stuff from which natural things are formed, how their forms differ from those of artifacts, the various agencies that produce them, and the ways in which they attain ends intended and achieved through nature's operations.

3. Matter as Nature

If the matter or material cause of a natural entity is the stuff from which it is made and remains in it, precisely what that stuff is invites clarification. The wood from which a chair is made is apparent on the surface. It may be seen, for example, as oak or cherry. Not so simple is identifying the material out of which an oak tree or a cherry tree is made. The same applies to an element such as lead, or an animal such as a horse. Is there a basic stuff out of which natural substances are made and that remains in them?

Philosophers and scientists have been pondering this question for some twenty-five centuries. The best answers have been obtained from studying the various changes natural substances undergo as they are generated out of preexistent materials or broken down into them. The earliest proposal was a four-element theory. In this theory the basic postulated entities were fire, air, water, and earth, and these were used to explain all terrestrial phenomena. To them were added a fifth element, a quintessence known as aether, to explain phenomena in the heavens. The result was a very durable explanatory scheme that lasted for twenty-four centuries -- all the way to the end of the eighteenth century.

It was around 1808 that the chemical revolution brought in hydrogen, oxygen, nitrogen, carbon, and other substances as better candidates for elemental status. These provide the common answer given by those who have studied modern science -- : the chemical elements are the basic stuff of the universe. But the shortcoming of that answer becomes apparent as soon as we ask how basic this stuff can be. Put in another way, what is the stuff of which these elements themselves are made? And, if electrons, protons, and neutrons is our answer, well, what is the stuff of which they in turn are made? And so on. The jury is still out on any final answer to that type of question.

More will be said about the material substrate of natural substances in our next lecture. For now it may suffice to note that Aristotle spoke of the ultimate material component of natural entities as "first matter" or "protomatter" (Lat. materia prima. Gr. hule prote). He thought of it as a type of conservation principle that persists through all natural changes in the universe.

Somewhat unexpectedly science has come to develop a similar conception in recent years. No longer are scientists searching for one final particle that is the ultimate building block of the universe. Instead they are focusing attention on factors that are conserved in all the changes that take place in the world of nature. Probably the most successful factor they have unearthed to date is owed to Albert Einstein, the concept of mass-energy.

I shall be using mass-energy in these lectures to gain some insight into prime matter or protomatter as the basic potential principle underlying all changes in the universe. Both of these concepts are different from those of ordinary experience and are difficult to conceptualize. But no longer are we to think of matter as the passive and inert component of things it was previously thought to be. Rather it is a potency that lies at the base of the most cataclysmic upheavals taking place on our planet as well as those occurring in the remote depths of space.

4. Form as Nature

Returning to the causal model based on our artifact, the chair, we note that its form is intimately related to its matter. Form is the shape or figure the matter assumes when the chair is made, so that form becomes part of its being. Moreover, although the wood, say oak, was not always formed as a chair, as long as it was identifiable as oak it was always under one form or another. From this point of view matter and form are quite inseparable. This being so, one might think that both are equally unintelligible. Just as there is something mysterious about the basic matter of the universe, so one might think that form is unintelligible too. Not so! Though matter is to a large degree refractory to the human mind, form is surprisingly intelligible. It provides a window through which the world of nature is seen and through which many of the natures that inhabit it can be readily understood.

We can see this from the ways we speak about the natural objects, and not merely the artifacts, that fall under common observation. We are able to identify most of the animals, plants, and minerals with which we come in contact. We are also able to classify them in ways that show our awareness of the differences among them. Moreover, though many of these objects have a multiplicity of parts and are far from homogeneous in structure, we grasp them in a unitary way and ascribe one nature to them. It is this formality or form that we name and define as we become acquainted with the natural kinds in our environment.

How, then, may be characterize this natural form in a way that differentiates it from an artifact? Obviously the shape of a cow or a giraffe, even seen in silhouette, is a help in identifying it. In this respect it resembles the form of an artifact. But the shapes of organisms vary over a wide range from one individual to another, and even in one individual throughout time. This is true despite the fact that the natures underlying the shapes remain the same. And similar statements may be made about most of the quantitative and qualitative attributes that are found in natural substances.

So as to differentiate shapes and other accidental forms from the type of form that gives unity to a nature, philosophers label this a natural form or a substantial form -- a form that underlies its attributes and make it an enduring substance. Changing attributes and properties they then refer to as accidental forms. These are forms that modify the substance in various ways. Accidental forms may vary in degree, or in presence and absence, without affecting the basic character of the substance.

It is this natural form or substantial form that we apprehend when we grasps the nature of a thing and attempt to define it. Then it becomes a universal as described in our last lecture. It is given in sense experience, but it requires an intellectual process of abstraction -- the first degree of abstraction -- to be apprehended by us. When the universal is grasped, whether it is the nature of lead, copper, oak, mosquito, or kangaroo, it becomes appicable not only to this or that lead, copper, oak, etc., but to each and every instance of them. Were this not so, it would be impossible for us to have universal knowledge of the world of nature, and a fortiori any science of nature.

The simplicity and universality of the natural form should not obscure the many attributes and activities that derive from it and of which it is the inner source. To say that a horse is a mammal, for example, signifies that it belongs among vertebrates that nourish their young with milk secreted from glands of a special type. The entails a complex organism with structures and organs that function in interrelated ways to assure the well-being of the whole. Much more will be said about the ways in which activities originate within such natural agents in our next lecture. For now it need only be mentioned that the unifying form, no less than the underlying matter, is the inner source from which all such activities ultimately spring.

What has been observed thus far is applicable to natures found in common experience and readily apprehended by our senses. Special problems are posed by entities in the microcosm and those in the remote depths of space. Whether things such as quarks and black holes even exist, or whether they have natures in the same sense as the animals, plants, and minerals we generally know, are problems for the philosopher of science. The important point to note, however, is that we cannot start with such entities to construct a philosophy of nature. In our discipline we must proceed from the more known to the less known, not the other way round. And natural form is intelligible to us and provides the necessary starting point for the philosophy of nature.

5. Nature as Agent

Now we come to the third explanatory factor in our causal model, the agent or efficient cause. In the making of the chair we pointed to the craftsman as the principal agent. This was the case of one natural substance, a man, acting on another natural substance, say oak, to transform the oak into a useful artifact. The craftsman had the capability to make a chair because of motive powers lodged within his nature. These powers can serve to explain how he could be an efficient cause in the production of the chair. As it turns out, human beings are natural organisms that possess many powers and capabilities, and so they can serve as a paradigm for the investigation of agencies in nature.

It is natural for humans to think and to will, to speak and to write, but these are activities of the mind rather than of the body. The production of material artifacts, a work of the body, are also characteristic of humans. The example of chair-making can be extended indefinitely as one ranges through all the constructive, mechanical, and industrial arts -- the feats of engineering, the products of technology in our century. Man is a powerful agent who acts, directly and indirectly, on the substances around him, appropriating them and transforming them in countless ways to suit his needs and desires.

Similar instances can be adduced in the animal and plant kingdoms. Beavers build dams, birds build nests, and spiders build webs. In all these natural activities they use or affect objects with other natures to the benefit of themselves and their species. Animals give birth to young and plants bear seeds, thus serving as agents for bringing new organisms into the world. And through the balance of nature, fauna and flora convert chemical substances and direct solar energies to provide food and nutriment for a wide range of species. All living organisms, in their life processes, are so many agents that interact with their environment and produce changes in other things in the course of their development.

At the level of the nonliving, on the other hand, agencies are not so easy to identify. But modern chemistry has provided remarkable insights into the ways elements interact with each other to form compounds. Chemicals have affinities. Under proper circumstances they enter into combination with other substances, thus affecting them and in many instances giving rise to new natures.

Physical agents are frequently seen as exerting forces on objects and causing motions and changes of state in them. In this view, a force is itself an instance of an agent or efficient cause. Indeed, the use of the force concept in the physical sciences illustrates how pervasive agency or action is in the realm of the inorganic.

Physicists link forces with energies and fields, and these provide a further source of information about natural agents. Studies in high-energy physics yield four major forces that are believed to underlie all of nature's transformations. These are the gravitational force, the electromagnetic force, the strong force, and the weak force. They will be discussed in our next lecture. Each of them provides examples of ways in which the material components of the universe act on each other to produce the phenomena observable within it.

6. Nature as End

This brings us to the fourth and final factor in our causal analogue, the end or final cause. The Greek word for end is telos, source of our term teleology, and thus to the problem of teleology in nature. For Aristotle it was almost axiomatic that nature is teleological, that it acts for an end. In our day the problem takes on added importance because of the theory of evolution. If evolution is viewed as a natural process, does this not entail that it is a teleological process? Is not evolution goal directed, in the sense that higher and more developed species are not merely the result of chance but are somehow predetermined by nature?

To answer this and related questions, it can be helpful to distinguish three different meanings of the word "end," not all of which apply equally to natural processes. The first and simplest meaning is that of end in the sense of terminus. In traveling from "here" to "there," the "there" is the end of the trip, where the traveler comes to rest. In falling motion, the motion terminates when the heavy object arrives at a center of gravity. In the domain of the living, growth terminates when the organism reaches a state of maturity. Fleas grow, but not to the point where they reach the size of elephants. They stop growing when they reach a size fixed by their nature. Chemical reactions "go," but they also "stop," for example, when hydrogen and oxygen combine to form a stable molecule in water. Some heavy elements break down radioactively, but not indefinitely. The breakdown of uranium, for example, terminates at lead. So nature is more than an inner source of change and activity. It is also the source of permanence and stability. When such stability terminates a natural process, whether inorganic or organic, it is the end of the process and as such its final cause.

A second meaning of end or goal adds to the idea of terminus the notion that it is somehow a perfection or good attained through the process. In some instances of natural change this meaning is easily verified, in others it is not. Clearly in cases of organic growth the end product represents a superior grade of being over the stage at which it began. It is also more perfect, in the etymological sense of the Latin per-fectus, as that which is thoroughly made and possesses no de-fectus, i.e., is lacking in nothing it should possess.

In inorganic changes it is difficult to see how a compound is better than an element, or how an element of higher atomic number is better than an element of a lower. Perhaps one should differentiate here between processes that are good for a particular nature and those that are good for nature as a whole. Elements are good in themselves, and sometimes act to preserve their own being, as when sulphur crystallizes and so preserves its identity. But compounds may better serve the needs of the organic world. Plants and vegetables represent a higher stage of being than complex molecules. Yet their stage is lower than that of the animals that eat them and incorporate them into their substance.

If this seems true in the observable order of nature, it would be even truer in evolution, if this is indeed the work of nature. The successive production of higher and higher types represents some kind of progress -- a greater good or perfection attained over time -- presuming that the later types are not mere freaks or chance occurrences.

7. Cognitive Agents

The third meaning of end is more specialized still. It adds to the notions of termination and perfection that of intention or aim. This serves to identify the type of final causality found in cognitive agents. Animals and humans are natural agents of this type. Many of their activities are planned or intended in advance and so can be seen as end-directed from the beginning. A person building a house or a bird building a nest must have in advance some notion of what is intended. Otherwise neither builder would know how to gather the materials. There is a difference, of course, between the bird and the human. The bird does its work by instinct and makes its nest in a shape distinctive of its species. Humans are not so limited and can generate the multiplicity of dwellings known throughout human history.

Much of the difficulty with teleology in nature arises from seeing all final causality as intentional or cognitive, and not differentiating the cognitive from the terminative and the perfective. Medieval thinkers gave expression to this mentality with the expression opus naturae est opus intelligentiae: "the work of nature is the work of intelligence." If by saying this one means that every natural agent is consciously aware of the goal at which it is aiming, there is little evidence that this is so throughout the entire order of nature.

Yet the word intelligence can take on a variety of meanings. Note the way we speak of artificial intelligence in the present day. Perhaps in that way of speaking one could say that the double helix is programmed to replicate in a certain way and so "knows" how to do it. Or again, an asteroid "knows" how to find its path through the solar system without performing the calculations we make to predict its path. In this sense, natural agents seem to foreknow what they aim to achieve and so implicitly substantiate the claim that nature acts for an end.

Such considerations open up the complexity and mystery of final causality in nature, analogous to those already uncovered in investigating other lines of causality. Matter and form are easy enough to grasp in a general way, and yet understanding ultimate matter and unifying form presents difficulties of great magnitude. Natural agents are pervasive in the universe and some are readily identifiable. Yet cosmic agents are largely hidden and so have escaped detection for centuries. Final causes exert their influence in terminative and perfective ways, yet they too give rise to serious problems. Is there an ultimate goal to which nature tends? Is there an intelligence behind its operations that organizes its matter and its agents so as to achieve that goal? To answer such questions properly would take us considerably beyond the scope of the philosophy of nature. But simply posing them may perhaps illustrate why the study of nature is a fruitful starting point for one who wishes to become a philosopher.

8. The Inner Dimension

From the outset of our discussion two different but interrelated meanings of nature have been touched on. It is now necessary to focus on one of the meanings to make precise the sense in which nature may be spoken of as an "inner dimension," serving to differentiate natural entities from those seen as artifacts.

The two meanings may be approximated by noting that one captures nature when the word is written with a capital "N," the other when it is written with a small "n." The first designates the world of nature, the universe untouched by man but of which he is a part, the object of his consideration when exploring a primeval forest or when gazing into the starry heavens. It is this sense of nature that leads one to think of the Author of Nature or of Mother Nature -- some overarching principle that puts order into a vast collection of individuals to make of them a cosmos, an awe-inspiring system of the world.

The second meaning of nature focuses on the units that enter into this world system. These are the particular natures found in the universe that enable things to be classified into natural kinds. Questions relating to nature in this second sense turn our thought within, to a consideration of the intrinsic factors that enter into the individual's composition. This is the sense of nature captured by the expression "inner dimension." It is this meaning that is our focus of attention for the remainder of this lecture.

We think of the inner dimension of natural substances as constituted by matter and form as these have now been explained. Both matter and form are clearly components of nature as inner sources of the properties and activities of substances themselves. But we have also touched on agent and end as types of causality that are proper to nature and its activities. Apparently these additional causes are not merely "out there" but also somehow "inside" or "within" the entities that make up the natural world. We must first address the problem of how our "inner dimension" is constituted not merely of material and formal causes but of efficient and final causes as well.

In Fig. 2.1 we diagramed how four causes are involved in the production of an artifact. We used a circle and three regular polygons to show their distinction and the interrelationships between them. You will recall that an agent (A) acted on matter (M) and educed from it form (F) as the end (E) of the production. All four were seen as causes, separate but interconnected.

Let us consider now the analogous case whereby, in the order of nature and over a period of time, an adult female squirrel generates another adult female -- a mature organism of the same nature as itself. The agent here is the parent squirrel along with its partner's seed (A), the matter (M) is the gametes on which they work, actually parts of their substances, and the form (F) is the same in kind as their own, namely, the form of a squirrel. The offspring first appears as a zygote or embryo, but over a length of time it undergoes a growth or developmental process whose end (E) is the adult squirrel. The parents and their offspring thus share a common nature, even though their appearances will differ markedly over time.

This final situation may be diagramed as shown in Fig. 2.2 (p. 26 of The Modeling of Nature), now labeled "the inner dimension." It aims to show that nature, while primarily constituted of matter (M) and form (F) as the intrinsic causes that make the substance be what it is, also incorporates agencies (A) and the functions for which they are programed (E), all of which can be modeled by the corresponding causes of an artifact. Each cause serves as a determiner lodged within the specific nature as such and, to this extent, may be regarded as part of its inner dimension. The natural form (F), to be sure, is the dominant determiner, for it is eminently intelligible. So intelligible, in fact, that it can be grasped, even by a youth, to serve as a starting point to unravel the remaining three causal factors. All four causes then explain the complexity of that nature and the manifold activities to which it can give rise.

The circle in Fig. 2.2 represents the natural form (F). The regular polygons then designate the other three causes, the agent (A) represented by the triangle, the matter (M) by the square, and the end (E) by the hexagon. The diagram is only schematic. Its purpose is not to represent natures in general but only the particular nature of a higher mammal such as a squirrel. Even then the nature shown is not individual but is common and specific, common to the parents and offspring of a family and to the squirrel species.

In this representation the basic matter (M) is its nature. For now let us call this the mass-energy of each organism, the co-principle within it that makes it a material substance, capable of subsisting as an individual, initiating various activities, and being receptive of them. The natural form (F) is also the organism's nature. This is even more the nature than the matter. It is a complementary co-principle, activating the mass-energy and determining the matter, contracting its potentialities, as it were, to being a substance of a particular type. It then stabilizes the substance in such being, supporting its distinctive powers and activities. Among these powers is the nature itself as an agent (A), as a source of activity that includes the ability to replicate, to produce another nature similar to its own through the reproductive process. And finally, when this new nature is produced as the end of the process (E), the same nature terminates the process and so may additionally be designated its final cause. Thus all four causes come to be internalized within the concept of nature, even though only the material cause and the formal cause are spoken of as internal causes in the strict sense.

9. The Individual Natural Body

Thus far we have been talking about specific natures, the universals that are associated with natural species of various types. There are additional problems relating to individuals of those species, which I must treat briefly under the title, "The Individual Natural Body." Our aim is to show how one may regard matter and form as internal causes, while allowing agency and finality, which are usually regarded as external causes, also to be lodged within the individual natural body.

The structure of the individual natural body is diagramed in Fig. 2.3 (p. 27 of The Modeling of Nature). This shows that an individual natural body is a composite of substance and accidents. The substance of a thing is what enables us to locate it within a species, to tell what it is. The accidents of a thing are its individuating characteristics, and they enable us to recognize the thing as a particular individual of that species. The first composition is enclosed in double outline and labeled "substance." The second composition is enclosed in single outline and labeled "accidents and properties."

Concentrate first on the inner box, that of substance. As diagramed there, substance is shown as an inner core that is itself composed. The two components are both essential components, and they are matter and form. In our earlier diagrams we labeled these as M and F, but these letters are now replaced by PM and NF. PM stands for protomatter. NF stands for natural form or substantial form.

The accidents of a natural body are then shown in Fig. 2.3, arranged arbitrarily around the inner core. They are arranged into three categories: quantitative, shown in the diagram on the left of the inner core; qualitative, shown on the right of the inner core; and relative, shown beneath the inner core. The distinctive accident of the first group, the quantitative, is quantity, which is aligned with protomatter on the left of the diagram. The distinctive accident of the second group, the qualitative, is quality, aligned with natural form on the right of the diagram. The remaining accidents are then all grouped beneath the inner core in the middle of the diagram. Only two are shown there, relation and location, because of their bearing on the problem of motion.

Complete details on quantity and quality, and particularly how quantity is related to individuation and on how powers are qualities, will be found in The Modeling of Nature, pp. 27-31. Powers are substances' most distinctive attributes, because their numbers and kinds are the major indicators of the various natures that underlie them. How this is so will be the subject of our next lecture. It is also through powers that efficient causes and final causes are found operative in the world of nature. Powers solve the puzzle of how all four causes can be internalized within a natural body.

FIGURES

Fig. 2.1 The Causal Model

Fig. 2.2 The Inner Dimension

Fig. 2.3 The Individual Natural Body

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