§13. Epagoge
Aristotle is thought to have spent time in medical studies. His father was court physician to King Amyntas II of Macedon; both his parents came from Asclepiad families, whose sons traditionally practice medicine; and his writings refer knowledgeably to the art many times.
He anticipates the terms of the later polemic between medical empiricists and rationalists, coming down, as we might expect, in favor of hypotheses. Causes are never given in experience. We perceive qualities, not powers. Knowledge of causes is valuable for the physician’s art, as indeed for any art, and it takes reasoning, not just experience. He says it is “the duty of the natural philosopher to study the first principles of disease and health”; and that “most natural philosophers, and those physicians who take a scientific interest in their art, have this in common: the former end by studying medicine, and the latter base their medical theories on the principles of natural science.”112The rational doctor with his theoretical knowledge of causes exemplifies Aristotle’s distinction between medical techne and the mere emperia of the mere empiric. “We think that knowledge and understanding belong to techne rather than emperia, and we suppose the masters of techne to be wiser than mere empirics... because the masters of techne know the cause but the mere empirics do not.” The masters of techne are scientific, “not in virtue of
being able to act,” for mere empirics may be good physicians, “but in virtue of having the theory for themselves and knowing the causes.”113
Aristotle explains experience in terms of perception and memory. Recollections are always former perceptions; even recalling a thought recalls the sensible image thought requires. Memory is the memory of perception, and experience is much memory. “Sense perception gives rise to memory, as we call it; and repeated memories of the same give rise to experience (emperia); because memories though numerically many are a single experience.
And from experience, that is, from the whole universal that has come to rest in the soul, there comes a principle of art (techne) or of science (episteme)—of art if it concerns producing, of science if it concerns what is.” Repeating the account elsewhere, he says, “Now from memory, experience is produced in men; for the several memories of the same thing produce finally the capacity for a single experience. And experience seems pretty much like science and art.” But not quite the same. Experience is a way to art and science, a phase in their genesis. “Science and art come to men through experience.”114Aristotle explains memory (mneme) as a state (hexis) and an affect (pathe) belonging to a time-sensing power of the soul. The state involves the soul’s awareness of an image (phantasma) regarded as something that took place in the past. A memory is an image accompanied by the affect of pastness. The only difference between imagination, as a power of images, and memory, is this added affect of past time. Memory is not a process, not an activity; it is a state. Since irrational animals remember, memory is not a rational power. By contrast, recollection (anamnesis) is an active process controlled by thought. Experience emerges from memory without rational activity, standing midway between perception and the rational dispositions of art and science. Memory is a non-rational power we share with non-rational animals, but they are stuck there, while rationality affords our advance from memory to recollection, and from experience to art and science.115
Experience means many memories of the same, and arises from perceiving various qualities in things and remembering them. Animals can do that to some extent, people more so, relying on concepts and language. What distinguishes judgments of experience from art or science is not universality but explanatory power. Only universal judgments using explanatory concepts belong to art or science. Experience, even aided by concepts and language, is incompetent to discern the explanatory relevance of acquired facts.
Experience suffices for the judgment that all and only deer shed their antlers, but it is inadequate for the explanation, which Aristotle thinks depends on the supposed fact that of horned animals only deer horns are solid throughout, which makes them heavy and produces the need to shed them. No depth of experience will produce that explanation. It takes a power of insight to leap to the right explanation.116Experience is a source for science, but only by accommodating Aristotle’s canon of scientific demonstration, which is severe. Experience is always multiple, a multiplicity, what W D. Ross called a “coagulation of memories,” but I would describe as a mnemic synthesis, in which a universal is intimated though not yet inducted to the mind, remaining attached to a sensory manifold. Science is universal and involves understanding the explanation and not just the fact. The explanation cannot be just any plausible account; it has to be the real cause, which requires proof that the effect arises under no other conditions. No depth of experience leads to such a conclusion. Experience can show a series of facts; for example, that an herb cured Callicles and also Socrates. But it generates no insight as to the salient feature that distinguishes those who benefit from the treatment and those who do not. That takes insight, not just experience.117
The disposition of the soul by which we obtain such insight is logos (reason). We are not born with this logos, but acquire it, and what makes acquisition possible is our outsized capacity for perceptual discrimination and memory. Aristotle envisions a development, a genesis of logos. We begin with a tentative, unstable grasp of features. Concepts are adjusted and readjusted with experience, until finally we grasp features so interrelated that the elementary relations among them are evident. We then have a system of principles and concepts in terms of which we can understand, that is, demonstrate in syllogisms, what we know as fact by experience.118
This happens naturally, by nature, spontaneously in its season.
Of course, it is good that it happens; everything in nature, properly understood, is good. Yet the relation between experience and insight into principles is causation, not inference. The intellect is assumed to be so arranged that experience reliably causes insight into principles. As Frede observes, that is how Aristotle “can be an extreme rationalist and still consistently insist on the fundamental importance of perception for knowledge.”119Plato allows sensory perception to stimulate the recollection of forms. Falling in love with a beautiful body is a stimulus to pursuing the idea of beauty. But the eventual cognition of forms is all immaterial intellect with no involvement of the body or its images. “Man must needs understand the language for forms, passing from a plurality of perceptions to a unity gathered together by reasoning; and such understanding is a recollection of those things which our souls beheld aforetimes.” For Aristotle too, if all we had were sense perception, science would be impossible. But he allows more continuity than Plato did between experience and science, which grows from experience and never entirely abandons it. He even allows that “by watching the frequent recurrence of [some] event we might... possess a demonstration,” that is, attain what scientific proof requires, assuming that we have cultivated the logos-power to elicit the universal from singulars. Aristotle gives a name to this power of reason to extract the principle. “The way by which sense perception implants the universal is epagoge” Perception alone does not think and is not science, but perception that has passed through epagoge is an enhanced experience without which science is impossible. “It is clear that we must know the first things by epagoge, for that is how perception produces the universal.”120
Epagoge is sometimes translated “induction,” which is ambiguous between a causal operation and a logical inference: a conclusion can be induced, but so can an electric charge.
Aristotle again means cause, not inference. He explains epagoge as the power of “exhibiting the universal as implicit in the clearly known particular.” Perception is not science, but perception repeated and reflected (experience) and submitted to epagoge is a necessary condition of science. “It is impossible to come to grasp universals except though epagoge. But epagoge is impossible for those who have no sense perception. For it is sense perception alone which is adequate for grasping the particulars: they cannot be objects of scientific knowledge.” It may require many perceptions and much memory before experience actualizes a universal in the soul, but that is what has to happen for scientific knowledge of nature. If you ask Aristotle how it happens, he says it just does. “The soul is so constituted as to be capable of this process.” There is no “how”; the power that it is has this effect.121Aristotle seems confident that because we are rational beings, the principles of nature will stand out from our experience if we pay attention. The natural world has an intelligible structure, and we have a power of insight into its principles, a power that does not operate on its own, but develops with experience. This epagogic power to grasp principles in the sensory singularity of experience encourages Aristotle in the expectation that natural philosophy is a body of necessary truth. Nothing is hypothetical in such a science, but there is also no predictive power, no application. Science is an impartial true account of nature deduced from first principles, no more, no less.
He assumes that observations can survey all the cases and collect all the principles. “Epagoge proceeds through an enumeration of all the cases.” The difficulty is to know the negative, that there are no unexamined cases. The doubt that this question invites leads to others. How do we know that all changes have causes, or that causes of the same kind have effects of the same kind, or that one effect might not have several causes? Writing well before the Greek experience with skepticism, Aristotle is confident that these problems are manageable by reasonable assumptions about an order of nature we are meant to understand. “Men have a sufficient and natural instinct for what is true, and usually do arrive at the truth.”122
For Democritus, thinking and perception are continuous, not categorically different. For Plato, perception does not think. Only intellect thinks, and thinks best when purged of perception. For Aristotle too, perception does not think, though it nearly does; it begins to. It feeds the imagination, and science is impossible without those images. Aristotle’s position synthesizes Plato with medical empiricism, as Galen would do again five hundred years later. Perception does not think, but we use perception to think, and what we think on, with, or by is a sensory phantasm, an image or representation.