The Process of Induction

Experience, Reason, Knowledge, Grasping Universals

"All animals have an inborn discriminatory capacity, called perception. If perception is present, in some retention of the percept comes about, but in others not. ... When many such things come about, a difference comes about, so that some come to have reason from the retention of such things, and others not. From perception comes memory, and from memory (when it occurs often in connection with the same thing), experience; for memories many in number from a single experience. From experience, from the whole universal that has come to rest in the soul (the one apart from the many, whatever is one and the same in all those things), there comes a starting-point of art and of knowledge, of art if it deals with coming to be, of knowledge if it deals with being. Thus the states [that grasp first starting-points] neither belong in us in a determinate form, nor come about from other states that are more cognitive; but they come about from perception—as in a battle when a rout occurs, if one man makes a stand another does and then another, until a starting-point is reached. The soul is such as to be capable of undergoing this. ... [So it] is clear that it is necessary to cognize the first things by induction (ἐπαγωγῇ); for perception instills the universal in this way" (Posterior Analytics II.19.99b).

"By nature all men reach for knowledge. ... Animals are by nature born with the power of sensation, and from this some acquire the faculty of memory, whereas others do not. ... The other animals live by impressions and memories, and have but a small share of experience (ἐμπειρίας); but the human race lives also by art and reasoning. It is from memory that men acquire experience, because the numerous memories of the same thing eventually produce the effect of a single experience. Experience seems very similar to science and art, but actually it is through experience that men acquire knowledge and art. ... Art is produced when from many notions (ἐννοημάτων) of experience a single universal (καθόλου) judgment is formed with regard to like objects. To have a judgement that when Callias was suffering from this or that disease this or that benefited him, and similarly with Socrates and various other individuals, is a matter of experience; but to judge that it benefits all persons of a certain form, considered as a class, who suffer from this or that disease (e.g. the phlegmatic or bilious when suffering from burning fever) is a matter of art" (Metaphysics I.980a).

"It would seem that for practical purposes experience is in no way inferior to art; indeed we see men of experience succeeding more than those who have theory without experience. The reason is a that experience is knowledge of particulars, but art of universals; and actions and the effects produced are all concerned with the particular. For it is not man that the physician cures, except incidentally, but Callias or Socrates or some other person similarly named, who is incidentally a man as well. So if a man has theory without experience, and knows the universal, but does not know the particular contained in it, he will often fail in his treatment; for it is the particular that must be treated. Nevertheless we consider that knowledge and proficiency belong to art rather than to experience, and we assume that artists are wiser than men of mere experience (which implies that in all cases wisdom depends rather upon knowledge); and this is because the former know the cause, whereas the latter do not. For the experienced know (ἴσασι) the fact, but not the wherefore; but the artists know the wherefore and the cause. For the same reason we consider that the master craftsmen in every profession are more estimable and know more and are wiser than the artisans, because they know the reasons of the things which are done; but we think that the artisans, like certain inanimate objects, do things, but without knowing what they are doing (as, for instance, fire burns); only whereas inanimate objects perform all their actions in virtue of a certain natural quality, artisans perform theirs through habit (ἔθος). Thus the master craftsmen are superior in wisdom, not because they can do things, but because they possess a theory and know the causes (Metaphysics I.1.981a).


"There are men that are doctors, we say, and others that are doctors' assistants; but we call the latter also, to be sure, by the name of doctors. These, whether they be free-born or slaves, acquire their art under the direction of their masters, by observation and practice (ἐμπειρίαν) and not by the study of nature—which is the way in which the free-born doctors have learnt the art themselves and in which they instruct their own disciples" (Plato, Laws IV.720a).
Over time as they become adults human beings naturally acquire the kind of cognition Aristotle calls "reason" in the the process he calls "induction."

This is an instance of teleological causation (change for the sake of an end). The end is the existence the unmovable first mover enjoys. In acquiring reason, human existence becomes like the divine existence of the unmovable first mover.

To understand how induction is an instance of teleological causation, the first step is to understand "reason" and the cognition Aristotle calls "experience."

Human Beings Acquire Reason

Aristotle works out his understanding of reason in human beings against the background of Plato's Theory of Recollection. As Platonist and Platonic critic, he thinks Plato was right in one way about reason but wrong in another. The human soul cannot exist separately from the body, but Aristotle does conceive of reason in terms of the possession of certain concepts and the knowledge that constitutes the possession of these concepts. In this way, Aristotle rejects the ontological thesis but accepts the epistemological thesis in the Theory of Recollection.

The natural process in which human beings acquire reason is what Aristotle calls "induction" (ἐπαγωγή). It begins with perception. Memory comes next. After memory, comes "experience." After experience, comes "reason" and the knowledge that belongs to reason.

To understand the role the cognition Aristotle calls "experience" (ἐμπειρία) in induction, consider the knowledge many students acquire in a geometry class: that the interior angles of a triangle sums to two right angles. No experience of looking at or touching triangles is a premise in the proof of this truth about triangles. So the experience of triangles the students had as children is not evidence for the knowledge. It might be, though, that such experiences are necessary for them to have the knowledge. If this is right, then the experience enables them to have the knowledge because it results in the possession of the concept of a triangle.

For Aristotle, the relation of the experience in induction has to the knowledge that belongs to reason is the same as it is in the example about triangles. It is enabling. The experience is not evidence for the knowledge that belongs to reason. Aristotle does not think human beings infer the knowledge by drawing conclusions from this experience. He thinks that the ability to make inferences and to draw conclusions is an ability human beings possess only once they have the reason, and the experience in induction comes before human beings acquire reason.

Experience and Reason

In the Metaphysics, Aristotle appeals to an example from the practice of medicine for an example to distinguish the cognitive ability someone possesses when he has experience from the ability when he has an "art" (τέχνη) and when he has "knowledge" (ἐπιστήμη).

The translations can be confusing, but the crucial point is that both these cognitive abilities involve a grasp of universals, whereas the ability acquired in experience does not. An "artist" (someone with an "art") has the ability to grasp universals in connection with "coming-to-be." Someone with "knowledge" grasps universals in connection with "being."

The example Aristotle uses to distinguish these cognitive abilities involves the two types of medical doctors in ancient medicine, the practitioner and the theorist.

The practitioner has a cognitive ability acquired in experience. He makes the "judgement that when Callias was suffering from this or that disease this or that benefited him, and similarly with Socrates and various other individuals on the basis of experience.

The theorist makes a different judgment: that "it benefits all persons of a certain type, considered as a class, who suffer from this or that disease (e.g. the phlegmatic or bilious when suffering from burning fever)." This judgment involves a graps of a universal.

The practitioner can make a diagnosis in circumstances in which the layman is more likely to make a mistake, but he does not grasp the universal the theorist knows is common to the patients who have a certain disease and benefit from a certain treatment. The practitioner does not conceive of the disease in terms of a universal, such as being phlegmatic. The practitioner notices the disease in terms of how his patients look. This ability is acquired in experience It is a matter of perception and memory, not the cognition Aristotle calls "reason."

Aristotle says that practitioners "know (ἴσασι) that the thing is so," but he is talking about the judgment the practitioner makes in the ordinary language used to talk about it. Strictly, though, because the cognition that characterizes the judgment the practitioner makes is a matter of experience as opposed to reason, it follows that this judgment is not a matter of "art" (τέχνη) or "knowledge" (ἐπιστήμη).

  "Knowledge (ἐπιστήμη) is not in the sensations, but in the process of reasoning about them; for it is possible, apparently, to apprehend being and truth by reasoning, but not by sensation.
  So it seems, Socrates.
  Then will you call the two by the same name, when there are so great differences between them?
  No, that would certainly not be right.
  What name will you give, then, to the one which includes seeing, hearing, smelling, being cold, and being hot?
  Perceiving. What other name can I give it?
  Collectively you call it, then, perception?
  Of course.
  By which, we say, we are quite unable to apprehend truth, since we cannot apprehend being, either.
  No; certainly not.
  Nor knowledge either, then.
  No.
  Then, Theaetetus, perception and knowledge could never be the same.
  Evidently not, Socrates; and indeed now at last it has been made perfectly clear that knowledge is something different from perception.
  But surely we did not begin our conversation in order to find out what knowledge is not, but what it is. However, we have progressed so far, at least, as not to seek for knowledge in perception at all, but in some function of the soul, whatever name is given to it when it alone and by itself is engaged directly with realities.
  That, Socrates, is, I suppose, called having opinion.
  You suppose rightly, my friend" (Theaetetus 186d).
The point is not that the practitioner has less clinical success than the theorist. The practitioner may have the experience that allows him to discriminate all and only the patients who have a certain disease and who will benefit from a certain treatment. What distinguishes the practitioner from the theorist is a graps of universals. The practitioner does not grasp "the why and the cause" necessary for the "knowledge" (ἐπιστήμη) exhibited in a demonstration.

It is common to think that knowledge requires the knower be in a special position with respect to the proposition he knows. Sometimes this is expressed by saying that knowledge requires justification, but for Aristotle what one might ordinarily accept as justification is insufficient. The practitioner can point to past success in treating patients whose disease he identifies in terms of a certain way they all look, but this is not enough for what Aristotle calls "knowledge." He thinks that one must grasp the intelligible features that underlie the sensible and figure in the account of what the disease is and why the treatment is successful.

Behavior Learned in Experience

Aristotle draws a parallel distinction between a kind of purposeful behavior learned in experience and the cognition that belongs to reason that he calls "choice."

In the Metaphysics, he says that some animals are "sensible" (φρόνιμα). These animals are capable of controlling their behavior by discriminating among things in their environment in ways that benefit themselves, but this behavior is not an exercise of reason. Human adults have both experience and reason, but children and animals are limited to experience.

"Now animals are by nature born with the power of sensation, and from this some acquire the faculty of memory, whereas others do not. Accordingly the former are more sensible and capable of learning than those which cannot remember. Such as cannot hear sounds (as the bee, and any other similar type of creature) are sensible (φρόνιμα), but cannot learn; those only are capable of learning which possess this sense in addition to the faculty of memory. Thus the other animals live by impressions and memories, and have but a [comparatively] small share of experience; but the human race lives also by art and reasoning" (Metaphysics I.1.980a).

"In the other animals choice does not exist, nor in man at every age or condition; for neither does deliberating and judgment about the why. It is possible that many have an opinion whether a thing is to be done, but not through reasoning(λογισμοῦ)" (Eudemian Ethics II.10.1226b21). So, according to Aristotle, there are two ways to engage in purposeful behavior. Some purposeful behavior is a matter of "experience." In human beings, however, because they have reason, some purposeful behavior is a matter of what he calls "choice" (προαἱρεσις).

We will consider Aristotle's understanding of "choice" in a subsequent lecture.

The Perfection of Reason

The "battle metaphor" Aristotle uses in II.19 of the Posterior Analytics is exceedingly difficult to interpret, but it suggests that he thinks that the reason human beings acquire in the process of induction does not grasp universals one by one in isolation. If this is right, then this grasp of universals does not take place without the advent of "knowledge" (ἐπιστήμη) of the necessary connections of consequence and incompatibility between these universals.

On this interpretation of the metaphor, presumably Aristotle also thinks the reason we first acquire can be improved and perfected. A human being first grasps universals in some basic domain and comes to deduce that certain further relations hold and thus in this way extends his knowledge of the domain. Further, as he becomes familiar with other parts of reality, he can grasp universals in other domains and in this way further perfect his reason.

In this way, "experience" (ἐμπειρία) occurs in two places in the life of a human being. As a human being becomes an adult, it is part of the process of induction that results in the possession of reason and its knowledge. It also occurs later in the life of a human being when he perfects his reason by extending its grasp of universals to other domains.

The medical practitioner, for example, grasps empirical generalizations about diseases and their proper treatments on the basis of his experience with patients. This experience is a matter of long and careful observation, but not all xperience is this kind of of experience. Human beings can reliably discriminate human beings from the other things they encounter in their lives. They acquire this cognitive ability in experience. It happens in the process of induction that results in the possession of reason, and the experience on the basis of which they have this ability is not the careful observation that give the practitioner his ability.

More of the Solution

Now we can see more of Aristotle's solution to a problem he finds in the inquirers into nature. The problem is to explain why the regular ways natural bodies of a given kind behave are good for them. On the explanations the inquirers into nature give, as Aristotle understands them, it a coincidence that the ways these bodies behave is good for them. Since what happens regularly over and over again is not a coincidence, he concludes that the "for something" is in nature and that the natural bodies have these behaviors because they are good for them.

Aristotle explains how the natural bodies have these behaviors in terms of their forms. The form is the organization of the material so that there is a body of the kind. The body has the potentials to behave in the ways that characterize the species because material organized in this specific way has these potentials. So, for example, the organization of the flesh and blood, and so on, as a rational animal gives a human being the potential for reason. In the natural process of "induction" (ἐπαγωγῇ), human beings naturally develop reason as they become adults.

Further, Aristotle thinks that this behavior in human beings is good for them and that this is not a coincidence. It is not that the human beings have this behavior because of their form and that the behavior happens to be good. Somehow the form is "for the sake of" this good.

Just what Aristotle has in mind is not easy to see very clearly, but we can make some progress if we turn to his cosmology and to what Aristotle calls the unmovable first mover.




Perseus Digital Library:

Plato, Phaedo, Theaetetus
Aristotle, Eudemian Ethics, Metaphysics.

Henry George Liddell, Robert Scott, A Greek-English Lexicon:
γνωρίζω, gnōrizō, verb, "gain knowledge of, become acquainted with, discover,"
ἐμπειρία, empeiria, noun, "experience"
ἐννοέω, verb, "reflect upon, consider"
ἐννοηματικός, ennoēmatikos, adjective, "notional"
ἔννοια, noun, "notion, conception"
ἐπαγωγή, (from ἐπᾰ́γω = ἐπι +‎ ἄγω),
καθόλου, (= καθ᾽ ὅλου), katholou, adverb, "on the whole, in general"
λογισμός, logismos , noun, "counting, calculation"
συλλογισμός, syllogismos, noun, "computation, calculation"
τέχνη, technē, noun, "art"

Charlton T. Lewis, Charles Short, A Latin Dictionary:
inductio, noun, "a leading or bringing into, introducing"

Arizona State University Library. Loeb Classical Library:
Aristotle, Posterior Analytics




"To say that it [induction] is somehow a natural process by means of which we arrive at first principles is to exploit Aristotle's generous conception of what is natural and to focus on just one aspect of it. This becomes particularly clear if we keep in mind that on Aristotle's view it also is the case that by nature we are meant to be virtuous and are thus constructed as to naturally be virtuous. Nevertheless, Aristotle also assumes that it takes a great deal of effort on our part to come to know the first principles in general (and thus to become wise), or even just the first principles in some domain. What is needed for this is a great deal of often highly specialized observation and of often highly technical reflections. But this should not obscure the fact that the insight, if it is an insight, does not derive its epistemic status from these observations and reflections which lead up to it. What makes it an insight is not the support it gets from observations or considerations, but that one finally sees in a way which fits how the features in question are related to each other and to other relevant features" (Michael Frede, "Aristotle's Rationalism," 172. Rationality in Greek Thought, 157-173).

"[Aristotle thinks] that organisms have to be understood teleologically, as naturally tending to achieve full development and perfection in their kind, unless handicapped or their development is thwarted. Since we [human beings] naturally do have reason and since reason functions best, and serves its function best, if we do have the requisite knowledge, he assumes that we must be constructed in such a way as to be able to acquire the knowledge reason needs to function well. And he, too, thinks that he can explain this by assuming that there is a process which leads, on the basis of perception and memory, not only to our having concepts, but to our having concepts which are adequate to the way things essentially are, and which thus provide us with basic knowledge about things, but also with the ability to think and reason about things, properly speaking, instead of, for instance, just having impressions or even generalized impressions of things" (Michael Frede, "Introduction, 14. Rationality in Greek Thought, 1-28).

"On Aristotle's view it does not seem to suffice for thinking [as opposed to experience] that we have a notion of, say, a human being which allows us, by and large, to distinguish successfully between human beings and other things; the notion rather has to be based on a sufficient grasp of what it is to be a human being, of the crucial feature or features of human beings, and of how these features are related to each other and to a whole network of features. ... To grasp what it is to be a human being, on Aristotle's view, is more than just to grasp what human beings have in common; it is to grasp something which figures prominently in the explanation of human beings and their behavior" (Michael Frede, "Aristotle's Rationalism," 164. Rationality in Greek Thought, 157-173).

"However obscure, and in their interpretation controversial, the details of his account of how we acquire concepts may be, it is abundantly clear from [Posterior Analytics] 100a12-13 that Aristotle does not envisage that the concepts are acquired one by one in isolation. However we interpret the battle metaphor, it seems clear that he assumes that we begin with a tentative and unstable grasp of the different features, which constantly threatens to collapse until we get a firm grasp on some feature such that, given the way the features are interrelated, our grasp of the whole group solidifies and stabilizes. ... We do not come to acquire these concepts piecemeal, but by a process of mutual adjustment with other related concepts, as a result of which certain elementary relations between features in the end seem evident. ... [Aristotle] does not appeal to some mysterious power of the mind to see directly or intuit features or forms, but to some complex process in the course of which our notions again and again are readjusted until they finally fit into a coherent and appropriately structured system of notions and corresponding beliefs in terms of which we finally can make sense of what know from experience" (Michael Frede, "Aristotle's Rationalism," 171. Rationality in Greek Thought, 157-173).


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