An account is given of the way in which we humans know. Other animals have only sensation, which allows for memory in some. The ability to remember gives rise to higher intelligence, allowing some to be taught.
Human beings have the ability to act systematically in pursuit of an end ("art") and reason, which allows us to have "connected experience." Experience is the basis of all human endeavor (a view known as "empiricism," which is opposed to Plato's "rationalism.") We can take a systematic approach to things only insofar as we are able to unify our perceptions of similar things into a judgments about things of that kind. An example is in the cure of disease: a treatment works in a number of like cases, and a judgment it has worked in all cases of a disease of a certain kind is the basis of the art of healing.
Experience is also basic to practical actions, more so than just the theory found in an art. For art is about what is universal, but action, like experience, concerns what is particular. The physician cures particular persons, not human beings in general. On the other hand, someone with experience without theory is at a disadvantage, for such a person does not know why his practice is successful. The theorist knows the "why," the cause of things. This is why we call the masters of a craft wise, and it is what enables them to teach.
The hierarchy of wisdom, then, is this: someone with mere perception, then someone with experience, then the master of a practical art, and finally the person whose knowledge is purely theoretical, directed at truth itself, rather than toward practical ends. In the Ethics (to be discussed later in the course), Aristotle claimed that the highest form of wisdom is purely theoretical, with no eye to action. In this sense, his view resembles that of Plato, though the objects of thought for Aristotle are not other-worldly. "Cearly then wisdom is knowledge about certain causes and principles."
All four of the desirable aspects of knowledge are satisfied through knowledge of the universal. A person can only know many things through knowledge of what they have in common, rather than by acquaintance with each one individually. The universal is also most difficult to understand, being most remote from the senses. (Again, Aristotle is agreement with Plato, as expressed in the Cave analogy.) The highest form of knowledge is that of "first principles," principles which are not derived from any others. These principles are universal, in that they express the causes of all things of a given kind. Someone who knows these causes can teach best. Finally, these first principles are most knowable, and they are sought by those who wish to know for the sake of knowing. So the highest knowledge is "a science that investigates the first priniciples and causes, for the good, i.e. that for the sake of which, is one of the causes." (Note once more that Aristotle follows Plato in placing "the good" at the top of the hierarchy of knowledge, but he interprets the good differently, as a worldly form which serves as the end of things.)
Even the earliest philosophers valued theoretical reason over the practical. They moved from practical matters, to questions about visible phenomena such as the motions of the heavens, to the question of the origin of the universe itself. They pursued these investigations from a sense of wonder, to know for knowledge's own sake. We can call this knowledge "free" in that it is not restricted by anything else.
Perhaps the God would be jealous of human beings seeking this noble end. But Aristotle assures us that this science is the most honorable of all, and "most divine" in two ways. It is the science it would be most appropriate for God to have, and it is concerned with divine objects. "For God is thought to be among the causes of all things and to be a first principle."
2. There are many ways in which something can be said to be, and so we use the phrase 'to be' homonymously. But there is one meaning (what some commentators have called a "focal meaning") of 'to be' which stands behind all of them. Here Aristotle makes an analogy with the word 'healthy,' which is also homonymous. A thing can be healthy insofar as it preserves health, produces it, is a symptom of it, or is capable of it. In each case, there is reference to some one thing, health. (Compare this with Plato's claim that there is one form of which many things are imperfect copies.) "So, too, there are many senses in which a thing is said to be, but all refer to one starting point." So a thing is said to be a substance (Socrates), or affection of a substance (snub-nosed), a process toward a substance (the act of procreation), etc. Just as there is one science of health, there should one science of what is, whose task is "to study all things that are qua being." As explained in the Categories, the primary mode of being is substance, so because a science "deals cheifly with that which is primary, and on which things depend," there should be a science of substance.
The science which investigates being as such must be "generically one." This means that there is a "first philosophy" which treats not of specific kinds of substance, but one which treats of substence generically, or in general.
Some of the general notions with which first philosophy deals are "same," "other" and "contrary." Each of these will have a "focal meaning" which is primary, as "all things which are one are referred to the primary one." We must say how the secondary uses are related to the primary. There are various sorts of possible relations: possession, production, etc. These will be a part of the science which deals with substance.
For example, are Socrates and Socrates seated one and the same? Only the philosopher asks this sort of question. Properties such as unity, otherness and contrariness as such are not the subject of other sciences. The other sciences have properties peculiar to them. Mathematics is the science of number, and it investigates properties such as oddness and evenness, more, less and equality.
Substance is primary in every way. It is primary "in formula," that is, in statement of what a thing is. If asked what is musical, one must answer that it is that individual singer. We know substances primarily and their properties secondarily. A substance must first exist, then be modified, so it is first in time.
The question, "What is being," is answered in a word: "substance." Philosophers have asked questions about whether being is one or many; hence their question is about substance.
3. Aristotle tells us that there are four main objects to which the word 'substance' has been applied:
The substratum (literally, that which lies below) is taken up first. The underlying reality of things lays claim to be substance. The substratum is what has qualities, e.g., that which is musical, so it is primary with respect to the things that are predicated of it. Further, we would not say of that which is white that it is a quality of any other thing. So "that which underlies a thing is said to be in the truest sense its substance."
But what is the substratum? There are three answers given:
It would seem that matter has the upper hand, for it is matter which has qualities (the bronze has the shape of a statue) and is not the quality of some other thing (we cannot say of a thing that it is the bronze). "When all else is taken away, evidently nothing but matter remains."
On the other hand, matter cannot be substance. For "the bronze" is not an individual, separately existing thing as substance is supposed to be. The matter always has some form or other. The compound of form and matter has the fatal problem that it cannot be primary because it is the result of something else. Only the form is left, but this is not easy to understand.
4. Aristotle considers next the essence. "The essence of a thing is what it is said to be in virtue of itself." The essence of a human being is not to be musical, for one is not musical simply by virtue of being himself. To state what such a thing is, we must provide a definition or formula. If we want to know what a surface is, we cannot answer that a surface is white, for being white is not what a surface is said to be in virtue of itself. Nor can we say that its essence is to be a white surface, since the definition would be circular.
As Aristotle had stated in the Categories, a substance can be categorized in many ways. A man is tall, sleeping, etc. Is there an essence of "tall man" or "sleeping man?" Aristotle states that probably there is not, since "tall man" is not a "this," and hence not a substance. The definition of a substance must be something primary, which does not involve something being said of another (being tall, being asleep). The only thing that will have an essence is a "species of a genus." Thus we can say that a human being has an essence, because humanity is a species of the genus "animal." We can say something about what is not substances, e.g. "what" it is to be musical, but again, this is not primary.
5. In one sense, only substance can be defined: its essence can be given a formula. We do give formulas to other things, but these formulas are never primary. We can define "snub-nosed" in terms of "nose" and "concavity," The quality "snubness" is problematic in a couple of ways. It depends entirely on being a qualification of "nose" in the way "male" depends on "animal." And the composite "snub-nosed" cannot be defined without circularity. For to be "snub" is to be a concave nose, so "snub-nosed" would mean "concave-nosed nose."
6. Is a thing the same as its essence? If essence is substance, then the answer will have a bearing on what substance is. A thing characterized in terms of its accidental attributes is different from its essence. "Tall man" is distinct from the essence of the thing, for otherwise to be a man would be to be a tall man. (Aristotle does admit that in one sense the essence and accident are the same, for to be tall is the same as to be the quality tall.)
A more interesting case is when substance is identified with forms (or "Ideas"). Is the essence of triangle the same as the form triangle? Aristotle replies that it would have to be. If not, then there would be something else besides the form which makes triangle what it is. To know what triangle is, one must know more than the essence, yet we say that we know a thing when we know its essence.
Another problem with separating the essence from the thing is that now the essence (say, horse) would itself have to have an essence. This process would go on to infinity, which is impossible.
10. The discussion turns to the question of the parts of substance, and as usual, Aristotle finds many ways in which one can understand what he is seeking; in this case, how the parts of the definition of a thing are related to the parts of a thing. Sometimes the formula of a thing (a syllable consists of a certain group of letters) expresses the parts of the things (the letters which make up a syllable), and sometimes it does not (a circle is defined as a figure each of whose points is equally distant from its center, but the parts of the circle are sections of the circumference and are not mentioned in the formula). In the thing, the parts are what make up the whole (a finger is one piece of a human body), but in the formula of the thing, the parts cannot be understood except in reference to the whole (a human being is more basic than a finger), in that the whole explains the part (a finger makes no sense except as the limb of an animal, and the animal can exist without a finger).
One sense of 'part' is that which measures the quantity of a thing, as when an inch is considered a part of a foot. But this does not apply to substance. If we consider the parts of substance to be matter, form and the composite of the two, we can think of matter as a part of substance. It is a part in the sense that it is an ingredient in the particular primary substance: the bronze is part of this statue. But in another sense it is not a part. For what the statue is, is defined by the form. But the matter is no part of the form.
In stating that the whole is more basic to the part, Aristotle had stated that while a finger is a part of a human being, its definition can be given only by reference to the whole human being of which it is a part: "a finger is such and such a part of man." In this respect, we think of the human being as a kind of thing, according to its essence or form. So in the definition of the form, the whole is more basic than the part. What is distinctive about the finger is that it is a material part of the human. If we ask about the parts of essence of the human being (which for Aristotle is the soul), we find that the parts of the soul are prior to the body itself. (Recall that Plato had stated that the parts of the soul include reason, appetite and spirit.)
So the question as to the the relation of the animal to the parts of the animal is ambiguous. If we think of the soul as the animal itself, we must think of it as composed of the parts of the animal, but if we think of it as form, then whole is more basic than the parts.
11. So which parts are of the nature of matter and which of the nature of form? A circle may exist in bronze or stone, and these material are not part of its essence. And since the soul of a human is always found in the human body ("in flesh and blood"), we try to think of the soul apart from it, "but because man is not found also in other matters we are unable to effect the severence" of the form from the matter in which it is found.
Aristotle now enunciates his main point of disagreement with Plato: "to bring all things thus to Forms and to eliminate the matter is useless labor; for some things surely are a partiuclar form in a particular matter, or particular things in a particular state." For example, we cannot think of the soul apart from the body, for the definition of an animal (which has a soul) include that of movement, which requires a body. In effect, an animal is something that can move itself, and a hand is part of what fulfils the bodily function of self-movement.
Even the objects of mathematics, which are not perceptible, "must have matter; for there is some matter in everything which is not an essence and a bare form but a 'this.'" The matter in which a semi-circle exists need not be perceptible.
The soul is the primary substance and the body is matter; the compound of both is the human being (which is an animal). Socrates can be understood as the soul or the concrete individual.
12. We define things through a genus (animal) and what differentiates that kind of things from other members of the genus (perhaps "two-footed"). The attributes making up a definition must be one and not many, to make the definition a single formula.
To define something properly, we must sub-divide the differences. We should not define a human being as an animal which is both two-footed and without feathers (the second distinguishing us from birds.) Rather, we should divide the attribute of having feet into kinds, as having cloven (divided) feet or not, since "cloven-footedness is a form of footedness. And we always want to go on till we come to the species that contain no differences." The last difference is the substance of the thing.
The problem with the alternative (not sub-dividing the differences) is that in that case, the order of the differences would be important; and it should not be. Suppose we say that the human being is an animal endowed with feet and distinguish it from other animals by its having two feet. The reverse order would be that a human is an animal with two feet, endowed with feet. But the latter is now redundant.
13. To return from definition to substance: we have seen that both the matter, the form (essence) and the composite lay claim to being substance. The universal (animal) is also considered substance. To be an animal is common to many things. If it is the substance of all these things, it is not substance, not a "this." But if it is the substance of just one, then all the things will be it.
The universal is always predicable of a subject but a substance is not predicable of anything (see Categories).
Is there another way in which a universal can be substance? Perhaps it is present in the essence, just as the essence is present in the substance. But how could this be possible? The universal could not be a quality or accident of the substance, for then it would be prior to and separable from substance (and qualities are not). Further, the universal would be a "substance in a substance," which is absurd. So no part of the definition is itself a substance (neither animal nor rational, which make up the definition of a human being, is a substance). "No animal exists apart from the particular animals, nor does any other of the elements present in formale exist apart."
The bottom line is that a universal is a "such" and a substance is a "this." Aristotle alludes to the "third man" argument, which greatly troubled Plato. If triangle itself (the universal) is a "this," then what is it that relates it to individual triangles? There must be some third thing. Then what relates that third thing to triangle itself, etc?
15. Substances in the sense of the composite can be destroyed, while in the sense of the form cannot ("the being of house is not generated, but only the being of this house"). There is no definition of an individual substance (Socrates), as there is definition of the essence (human being). The individual can pass away and change its qualities, but the definition is fixed.
A Platonic form cannot be defined, either. To define it, one must use words, which signify universals, hence applying to more than one thing. For example, "triangle" would have to be defined as consisting of lines, which are also had by squares.
17. Another way to look at substance is as a "principle and a cause." While we can ask why a substance has a certain quality (being musical), we cannot ask why it is itself. We cannot ask why a human being is a human being, but we can ask why a human being is a certain sort of animal. And we can ask why a body in a certain given state is a human being. What makes the matter of this body that of a human body?
There are two ways in which things can be composed: as a mere heap or aggregate, and like a syllable, which is more than the two parts taken together. Flesh is not merely earth and fire, for when it is broken down into its elements, it no longer remains flesh. It is the form or nature which is the principle which unites the elements
There are three kinds of substance. The first division is into the sensible and the insensible. Sensible substances consist of that which is eternal (the substance of the heavens) and that which is perishable (that of the things below the moon). These are the subject of natural science. Insensible substance has been considered in various ways by the philosophers: for Plato it is forms (including mathematical objects), while for the followers of Pythagoras it is the mathematical objects alone. There may be a separate science of these.
6. Sensible substances are moveable, but if there is an insensible substance, it cannot be the subject of motion. Aristotle asserts that there necessarily is an eternal immovable substance. Just as time cannot come into existence or pass away, neither can motion, since the two are intimately related. Time is continuous and so are movement. The only continuous movement is circular movement.
The movement of substance must be explained, and Platonic forms will not do the job, because they are inactive. Further, even if active, the must exist actually rather than potentially. And it must be immaterial, for anything material is perishable. So what explains the movement of substance must be eternal, immaterial, and purely actual.
It may seem that the purely actual is impossible, since every action requires a potential to act. But nothing can exist on the basis of pure potentiality only. There must be an actual cause.
Plato and Leucippus (the atomist) claim eternal actuality, on the grounds that there is always movement. But they cannot explain movement. For on their view, movement would just be random. But there must always be a cause of movement, either by nature, by force, by thought, or by some other means. Plato cannot say what kind of movement the primary movement is. (For Leucippus, the movement of atoms is parallel until a swerve causes them to bounce off one another.)
The origin of the universe is no different from what exists now: there was no transformation from one condition (chaos or night) into the present one. For the prior state would have been one of potentiality only. So "something must always remain, acting in the same way." But because there is generation and corruption, there is something else acting in different ways. Aristotle explains this by stating that the action of the constantly acting substance directly affects the things which act in different ways.
"There is, then, something which is always moved with an unceasing motion, which is motion in a circle." This thing is the heavens. Since it moves, there is something which moves it: a mover which moves without being moved. A model of such movement is"the object of desire and th eobject of thought" which is the same: the good.
The ultimate explanation of motion, "that for the sake of which" is fond in something unmoveable. It cannot be otherwise than what it is, unlike the heavens, which need not move. "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."
The life of this actuality is the best: it is eternal while ours is transitory, and it is a pleasure. Thinking and perceiving are the most pleasurable activities, and the best thought deals with what is best in itself. The act of contemplation is what is most pleasant and best. The actuality of thought is life, so the unmoved mover is living, good, eternal; it is God.
This substance is without parts and indivisible, as well as being infinite, since it produces motion through infinite time. It is always active and not subject to change.
8. How many such substances are there? The previous philosophers have said nothing about this question.
Aristotle seemingly allows for there being other substances besides the one which moves the universe as a whole, e.g. those which move the planets.
9. It has been stated that the unmoved mover, God, is a thinking substance. But what does God think? To think nothing is tantamount to sleeping. If its thinking depends on something else as a stimulus, it is not the best substance. So what does it think? What is most divine and precious and unchangeable. This can only be itself. The thinking of the divine being is "a thinking on thinking."
This distinguishes divine thought from the human modes of "knowledge and perception and opinion and understanding," all of which have something else as their object. The only way in which a thought can be pure, about something immaterial, is to be concerned with essence. In an immaterial being, the object of thought will be the immaterial being itself.
What has no matter is indivisible. Divine thought is eternal.