The Scientific Research of Aristotle

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The Scientific Research of Aristotle



Breadth and Scope. In Aristotle there is a consistent pattern of deliberate, conscientious research on as broad a range of scientific fields as were recognized in antiquity, along with the creation of entirely new fields that had previously been unknown: logic, epistemology, cosmology, medicine, physiology, psychology, biology, zoology, botany, optics, acoustics, physics, dynamics, mathematics, astronomy, rhetoric, political science, ethics, and literary theory. Roughly 30 of his more than 150 books have survived. It should also be remembered that Aristotle was as deeply committed to teaching and cooperative work as he was to independent research. Just as important as his own writings, therefore, is the long tradition of scientific research that he set in motion and that continued to operate through many later generations of researchers, teachers, and students at the Lyceum.

Rules of Logic. Aristotle gave a remarkable degree of attention to the language of science and the structure of scientific claims. This approach was partly his response to the epistemological problems Greek philosophers and scientists had faced for at least one hundred years. It will be remembered that in the early fifth century, Parmenides profoundly influenced the direction of Greek science and philosophy by using the new tool of logic to construct an argument that made rational sense but at the same time seemed to contradict everything the five senses suggested about the world. Whether one supported or rejected Parmenides’ argument, all subsequent thinkers nonetheless at least had to conform to the same rules of logic he had used.

Apodeixis. Aristotle’s concern with scientific language was partly also his own recognition that claims must meet rigorous criteria and standards in order to be true. If epistêmê (scientific knowledge) is genuine, after all, it must be based on apodeixis (valid proof). How, then, is it possible to recognize when a proof is valid or not? Are there rules that govern how valid proofs are put together? Are there logical steps that can be taken to test an argument for fallacies and inconsistencies? Are there clear, objective measures that can be applied to any given claim in order to refute it if it is false and confirm it if it is true?

The Tool. In a group of books known collectively as the Organon (circa 335 b.c.e.), Aristotle carefully analyzed these and similar questions. The result of his efforts is a finely detailed and rigorously argued exposition of the nature of reasoning. Here, and for the first time in any consistent and comprehensive way, he established the structure of valid, logical demonstrations and mapped out the shape of different kinds of premises—axioms, definitions, hypotheses—that provide the starting points for scientific claims about the world. He categorized types of arguments, investigated their forms, distinguished between abstract and empirical claims, and spelled out the basic rules an argument must follow in order to be logical. He then went on to determine what degrees of certainty each different branch of science was capable of giving, based on the kinds of proofs it was able to offer for its claims. The Greek word organon means “utensil” or “implement,” and in this painstaking work on the grammar of proofs, Aristotle indeed fashioned a tool that has shaped and continues to shape all later scientific discourse.

Criteria. For Aristotle, scientific knowledge is knowledge of the essential aitiai (causes) of any given thing. These causes are four in number, and in the case of any given thing it is necessary for all of them to be investigated and identified before true knowledge of that thing is possible. A valid, scientific account of something—whether it is inanimate (stone, water, spoon) or living (tree, animal, person), artificial (statue, table, machine) or natural (catfish, flower, embryo)— must fully explain: what it is made of; what shape or form it has; what made it what it is; and what purpose or function it serves.

Four Causes. These four criteria correspond to what are usually termed the material cause, formal cause, efficient (moving) cause, and final (telic) cause. They form the basis not only of Aristotelian physics, but also of his understanding of each and every thing and event in the world as a whole. They provide the basic answers to every question that can possibly be asked, from why a rock falls when dropped to what kind of life a human being ought to live. For example, a chair mostly has wood as its material cause; this is what it is made of. Its formal cause is what makes this mass of wood a chair and not, say, a bookshelf or a coatrack or a desk. In a word, the formal cause accounts for its shape, which clearly does much to define what any given lump of matter is. This chair was made in a factory by a worker, who thus provided its motive or efficient cause, namely, the series of acts by which the wood took on its shape. Finally, this chair was made for a specific purpose—its final or telic cause—which is to support persons comfortably as they sit.

Nature. Of course, the same truths hold for natural no less than artificial things. For instance, an acorn’s material cause is the woody stuff it is made of. Its formal cause is identical with the shape it has, which distinguishes it as an acorn and not, for example, a pine cone. Its efficient cause is the oak tree that produced it. (Notice here that the efficient cause is not necessarily the same as a human agent; it does not matter that the tree was not conscious of producing the acorn.) Last, its final cause is the goal toward which the acorn naturally tends, namely to grow into an adult oak itself.

Interpretations. Obviously, the idea of “cause” is somewhat narrower for many people than it was for Aristotle. People generally mean by it the individual or thing that directly produces a certain effect. That is to say, people tend to identify cause with what Aristotle calls the efficient cause. His idea of material and formal causes was meant as a direct response to Plato, whose philosophy of idealism made the ideal Form alone real and entirely detached from matter. For Aristotle, on the contrary, form and matter are inseparable. Although the word dog can be defined in a universal way, so as to include all real dogs in its description, there is still no ideal Dog apart from actual, living ones.

Final Cause. By far the most important of the causes for Aristotle, however, is the final or telic one—from the Greek word telos, meaning “end” or “goal.” Its sense is clear in the case of an artificial thing like a chair, since here the final cause is identical to the purpose or function for which the craftsman made it. Final causes also operate in the world of natural things, as in the case of the mature oak that is the ultimate goal of the acorn’s development. There is a major difference between the final cause of artificial and natural things, however. As far as the natural world goes, Aristotle firmly insists that no god exercises providential control over things and that nature itself also has no deliberate, conscious aim. That is to say, there is no equivalent in nature to the craftsman in the realm of art and manufacturing.

Immanent Teleology. The different ends toward which natural things grow—seeds into plants, for instance, or children into adults—are instead internal or immanent in the things themselves. Acorns naturally become oaks, not pine trees; penguins give birth to penguins, not mice. Democritus and the Atomists had claimed that all things in the world are the temporary result of purely random atomic collisions. Atoms bump into each other by chance and stick together to form certain objects, which break up when a stronger outside force splits them apart again. On the contrary, Aristotle claims that each and every natural thing exhibits a genuine purposiveness. Propelled by an inner drive—an immanent teleology—each moves steadily toward realizing its own specific kind of perfection. Each strives to actualize its innate potential.

Actual v. Potential. The distinction between what is energeia (actual) and what is dunamis (potential), in fact, was the key to Aristotle’s approach to the old Parmenidean dilemma of change. The puzzle had already been occupying Greek thinkers for more than a century: How can something come into being? Not from nothing (“what is not”), since nothing does not exist. Not from something, for whatever already exists is already in existence, and therefore has no need to come into being at all. Aristotle’s concept of dunamis neatly cuts through that logical knot. An acorn, for example, indeed is an oak, at least in the sense that it has the potential to grow into one; while in another sense, it is not actually an oak at all. It has the dunamis to be something else, even if this other something has not yet been actualized in the world. The concept of potential thus lets something come into being from nothing, namely from what does not really exist yet. Change— the movement from being potential to being actual—is logically possible after all. The evidence of the senses, which show us a world of constant change, is finally vindicated!


Aristotle’s description of the “navel-string” links embryo to placenta in a species of dog-fish called the “smooth shark.” Disbelieved for nearly two millennia, its existence was finally confirmed by researchers in the middle of the nineteenth century.

The so-called smooth shark has its eggs in between the wombs, like the dog-fish; these eggs shift into each of the two horns of the womb and descend, and the young develop with the navel-string attached to the womb…. The navel-string is long and adheres to the underside of the womb—each string being attached as it were by a sucker—and also the center of the embryo in the place where the liver is situated. . . . When young, the embryo has its head pointing upwards, but downwards when it becomes strong and has completed its growth. Males are generated on the left-hand side of the womb, and females on the right-hand side, and males and females on the same side together. If the embryo is cut open, then its internal organs (such as the liver) are found to be large and supplied with blood, just as in quadrupeds.

A passage from Aristotle’s description of the development of a chicken embryo, another classic example of meticulous empirical observation:

When the egg is now ten days old the chick and all the parts are distinctly visible. The head is still larger than the rest of the body, and the eyes larger than the head, but still sightless. The eyes, if removed about this time, are found to be larger than beans, and black; if the outer membrane is peeled off, there is a white and cold liquid inside, which glitters quite a bit in the sunlight, but there is no hard substance at all. Such is the condition of the head and eyes. At this time also the larger internal organs are visible, along with the stomach and the arrangement of the viscera; and the veins that stretch from the heart are now close to the navel. A pair of veins extends from the navel, one toward the membrane that envelops the yoke—which, by the way, is now liquid—and the other towards the membrane that contains both of the others: namely, the membrane within which the chick lies and the membrane of the yolk, along with the intervening liquid. On the tenth day the white is at the extreme outer surface, reduced in quantity, glutinous, firm, and with a pale color.

Source: The Complete Works of Aristotle, The Revised Oxford Translation, edited by Jonathan Barnes (Princeton: Princeton University Press, 1984).


J. L. Ackrill, Aristotle the Philosopher (Oxford & New York: Oxford University Press, 1981).

Jonathan Barnes, Aristotle (Oxford & New York: Oxford University Press, 1982).

D. R. Dicks, Early Greek Astronomy to Aristotle (Ithaca, N.Y.: Cornell University Press, 1970).

Pierre Pellegrin, Aristotle’s Classification of Animals, translated by Anthony Preus (Berkeley: University of California Press, 1986).

Samuel Sambursky, The Physical World of the Greeks (London: Routledge & Kegan Paul, 1956).

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The Scientific Research of Aristotle

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