“Realism” is an ontological position that states that theories about nature describe nature as it really is, independent of our existence. “Instrumentalism,” on the other hand, is a position that states that theories are merely good tools for prediction, but do not necessarily indicate the way the world is actually constructed. Apply these two categories to ancient Greek astronomy. Can we classify certain astronomers as “realists” or “instrumentalists?” What would be the advantages and disadvantages to both approaches?
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The two ontological positions of ancient Greek astronomy, realism and instrumentalism, had within themselves their own unique advantages and disadvantages. The ancient Greek astronomers implicitly classified themselves through their written works as supporting one school of thought over the other.
Ontology, defined as the study of Being; quite literally taken, this compound of two Greek roots means the study of existence; it has come to connote a philosophical position on the Real nature of the universe, or the way things really are. Everyone has an ontological position, of course: all sorts of ordinary people depend on what they believe to be real throughout the course of every day. They depend on the reality of food and the real, solid nourishment it provides for their bodies. However, they do not necessarily consider the question of Reality (or Being), nor do they need to understand philosophical underpinnings to understand that when their stomach growls, they are hungry, and that food is the means of alleviating hunger.
Some thinkers, however, have drawn the conclusion that the nature of the world as it really exists, is vitally important--perhaps even more important than practical means to everyday ends. Many of them have come to doubt the ability of perceptive human nature to accurately represent the nature of reality and have subsequently begun various quests seeking more reliable bases of understanding.
This simply drawn example can help to represent the divergence between physical and mathematical astronomy among ancient Greek scholars. Where physical astronomical philosophers sought reasons, answers, and the accurate model of the universe, mathematical astronomers sought accuracy in celestial prediction for practical use. To put it yet another way, the mathematical astronomer used study as a means to an end but did not seek the initial cause of the means. On the other hand, the physical astronomer may have considered the search for causes of celestial phenomena as all-important.
These categories, in this case, will be referred to as "realism" (the physical astronomer's position) and "instrumentalism" (the mathematical astronomer's position). Like all categories, however, they define themselves by historiography. Superficially imposed, they may or may not represent the ancient astronomical natural philosophers with any accuracy.
Realism attempts to seek out the truth of character of the universe, to use material observation and rational hypothesis to reach conclusions about the way nature functions. Keeping the focus of natural philosophy on the subject matter itself, the objective world, Realism does not deny the usefulness of natural knowledge, as long as it stems from an accurate model of nature. The study of nature under realism, if not advanced independently of practical concerns, at least retains the attempt to obtain accurate information about the way the world works as its goal.
Nevertheless, scientific inquiry does not take place solely for its own sake; human ingenuity has devised applications for knowledge about the world. This fact has led many to view scientific activity as a means to an end. From this contrasting point of view comes the ontological position of instrumentalism.
Instrumentalism concerns itself first and foremost with introducing some semblance of order into naturalistic observations, so that they might be predicted. If natural phenomena can be reliably predicted based on observation, then those observations become more useful. When one takes such a utilitarian perspective, the details of the physical nature of the universe become of secondary concern. What matters most is the development of models of nature that faithfully account for phenomena.
The two positions, while ontologically different, may help further each other’s goals. Presumably a model of a natural process, factually accurate and known so, would aid greatly in producing useful predictions. Also, the process of developing an effective predictive model may help bring underlying physical realities into question, leading to conceptual breakthroughs.
One of the first philosophers to look at is Plato. Plato acted as a transition between pre-Socratic philosophy and the post-Socratic philosophy that through Aristotle became famous. Before categorizing Plato as a realist or an instrumentalist, one must first look into his cosmology, defining it by his ontology, epistemology, and theories of the world's constructs. Unlike most philosophers of his day Plato questioned cosmological theories and also wrote his own. In the Timaeus, Plato wrote describing a piece of his ontology, “for nothing can come to be without a cause,” thus informing others of the premise to his cosmology. This passage within the reveals Plato’s view that everything has a cause and a reason for its existence. Later in the same work Plato stated, “finding the visible universe in a state not of rest but of inharmonious and disorderly motion, reduce to order form disorder.” He, then gives the action a reason: the creator wished for the world to have order “as he judged that order was in every way better" (Plato, Timaeus).
Plato’s cosmology to this point therefore provides an argument for a cause of nature's behavior. However, to judge Plato solely on his ontology without his epistemology could create a false classification. Plato argued for a world based on Forms in book IV of the Republic with the Allegory of the Cave. In the cave prisoners in chains saw nothing but the image of shadows cast by figures in front of a fire behind the prisoners. The prisoners represent all people; the shadows are the distortion of reality that human perceptions take for the true things. Plato believed that there were ideal forms that cast the shadows for people of Earth to see. Materially existent things such as animals, plants, or minerals, were imperfect copies of the perfect celestial forms from which their basis came. He thought that the things of earth could not give a person true knowledge. Only acknowledgement and examination of the perfect celestial forms could leave a person with true knowledge. Plato therefore argued that knowledge cannot come together by a strict study of nature but an understanding of what caused nature. In the bare idea of true knowledge, though, Plato demonstrated a belief in the ability of humans to achieve a genuine understanding of reality.
Finally, his divine (infinitely good, but not omniscient) craftsman (whom he called the Demiurge), “turned it [earth] into a rounded spherical shape… a figure that has the greatest degree of uniformity to be incalculably superior to its opposite.” Plato believed the earth spherical because the Demiurge caused it so. The perfection of the shape of the earth existed because all perfect things contain uniform circles or circular motion. Plato, arguing for the perfectness of uniform circular motion, thought circular motion was the motion of the celestial realm where the forms resided. Through both Plato’s epistemology: believing knowledge attainable solely by study of nature’s causes and forms, and his ontology: showing all things created for and by a cause, and his idea of the shape of the earth, Plato’s cosmology has a strong root in realism. “Everything that becomes or changes must do so owing to some cause.” Plato’s self-proclamation of his realism shines through, giving credit to cause as the source of how nature really exists independent of the existence of humans.
Eudoxus lived concurrently with Plato, his better-known elder. Like Plato, he accepted the idea of uniform circular motion with regards to the planets and other celestial objects. Seeking to solve the problem of retrograde movement of the planets, Eudoxus invented the first geometric model of planetary motion. Many astronomers, including Plato, contemplated why the planets appeared to randomly move backwards at times from their regular orbit in the sky and how could the planets move in such a manner and still move about with uniform circular motion. Eudoxus, thought as the first to do so, theorized that the planets moved in uniform circular motion within nested concentric spheres. The sophisticated idea, in its complexity, gave light beyond what had formerly been produced in the world of Greek astronomy. Aristotle later expanded Eudoxus' idea for his own astronomical theory. Moreover, at the time it plausibly explained how the planets could move backwards in any regularized fashion.
No evidence shows that Eudoxus developed a full-fledged cosmology from his theory, however and nothing shows that he wanted to. Eudoxus based his ideas on mathematical inquiry. His goal was not to produce a realistic model of the universe, but rather to account for irregularity by introducing plausible geometric order. Thus, if categories, such as realism and instrumentalism, must define the ancient Greeks astronomers then Eudoxus implemented himself as an instrumentalist.
Aristotle, once a pupil in Plato's Academy, classified as a materialist and empiricist, dually opposed the views of Plato. Aristotle maintained in his Physics that "since the aim of our investigation is knowledge, and we have knowledge of a thing only when we can answer the question about it 'On account of what?' and that is to group the primary cause...so that, knowing their sources we may try to bring all particular objects of inquiry back to them” (Aristotle, Physics, handout). Aristotle's overall goal in his systematic studies of the natural world compelled him to know what composed the nature of an object by itself, independent of humanities existence.
Consequently, Aristotle placed the foundation for one of the major benefits of Realism, the broad ontological group he generally falls under, by showing how Realism allowed natural phenomena the ability to be traced back to its source(s). Realism, also, takes into account that in order to study astronomy in a more concise way, other factors may affect the outcome and that these factors must have consideration for the overall understanding of astronomy.
For instance, Aristotle explained in his Physics that the importance of knowing what the sources are stems from the Realists' general concensus that people cannot recognize whether the changes occurring in the universe are effected by some outside force that should be taken into consideration for the overall conclusion to end up accurate. He explained this concept in a hands-on approach of the question of why someone walks. Aristotle insists the answer cannot stand on the basis of "to keep fit," and that be the only cause in of itself; other factors pertaining to the previous question must receive examination. He argued that "...the change being effected by something else, comes on the way to the end, as slimness, purging, drugs, and surgical instruments come to be as means: all these are for the end, but differ in that the former are works and the latter tools” (Aristotle, Physics, handout).
Carefully observing the language in the above quote enables us to see the implications of Aristotle quite clear. First consider the importance of 'sources' to Aristotle's understanding of nature. The construction of the question 'why does someone walk?' could have just as easily expressed as one of the main inquiries of ancient Greek astronomy of 'why do the planets go in circular motion?' This lead Aristotle into his theories on motion. For example, he thought that in the celestial realm there was a fifth element called quintessence or aether, which had a natural circular motion, the ideal perfect motion to ancient Greek astronomers. Additionally, nothing existed outside of the fixed stars except the Unmoved Mover. The planets and the Sun revolved around the Earth considered as the center of the universe. But everything that moved, according to Aristotle, must have been driven by a force. Consequently, there must have existed something unmoved, which caused the eternal motion in the celestial realm. Hence, Aristotle's belief in an Unmoved Mover: an indifferent deity that represented the highest good. The uniform circular motions of the cosmos moved in their manner because of the goodness of the Unmoved Mover.
It makes sense, then, that in addition to Aristotle's conclusions concerning motion, he came up with four fundamental causes: material, formal, efficient and final. The material cause: the object in questions composition, its essential qualities. For example, a tree's material cause is its wood, leaves, roots any 'treeish' quality. Secondly, the formal cause, the change that occurs in the object, of the tree moving came from a block of wood to a table, for instance. Then, the efficient cause, the carpenter in the case of the table, made the change in form of the thing or person. And lastly, the final cause, the purpose of the object which has canged form, the use of the table.
This whole conglomeration of causes can be directly applied to the 'sources' discussed previously. Examining the circular motion of the cosmos example again, the four fundamental causes clarified in more detail the essence of Aristotle's astronomy. He could not find satisfaction with just locating an answer to the material cause or any of the causes by itself, he wanted to produce the entire picture because he had convinced himself that this method of defining could only lead to true knowledge. He was not interested in predictions and ephemerdies, his theories were a means by which to find knowledge.
In Greek, physics is defined as 'nature.' Therefore physics for Aristotle was a study in the nature of objects. From this study came a basic principle of Aristotle's - the separation of physics into two categories: sublunar and celestial. Sublunar can be translated from Latin as 'under the moon,' and so it follows that sublunar physics investigated everything under the moon, while celestial physics examined everything from the moon upward. Aristotle's studies in this manner yielded many conclusions, including his speculations on the nature of the earth. He observed that the shadow on a lunar eclipse is always curved. He also noticed that to a person standing on a tower beside water and observing the ships leaving, the body of the ship will always disappear before the mast. This indicates that the ships are not sailing on a two dimensional plane. These physical observations led Aristotle to conclude that the Earth was indeed spherical. He also used theoretical implications to arrive at the same conclusion. He observed that the natural motion of any heavy object is to fall straight down towards the center of the Earth no matter what part of the world it is dropped at. Therefore, he determined that the Earth must be spherical. He did not use this knowledge toward any predictions, but rather appreciated the knowledge as its own end.
The most obvious distinction between the sublunar and celestial realms, according to Aristotle, was the variable of change. He believed that change was restricted to the sublunar, and that the celestial was completely unchanging. In his work On the Heavens Aristotle states, "in the whole range of time past, so far as our inherited records reach, no change appears to have taken place either in the whole scheme of the outermost heaven or in any of its proper parts" (Aristotle handout). Basing his universe on a geocentric system with the Earth at its center, the only object outside of the fixed stars was the Unmoved Mover, as stated previously. This Unmoved Mover, however, was not interested in the events of the world, just as Aristotle was not interested in the practical application of these theories, but instead sought the knowledge for his own edification.
Heraclides of Pontus (c. 390-after 339BC), a thinker contemporary with Aristotle, belonged to Plato's Academy during the leadership of Plato and that of his immediate successor, Speusippus. Heraclides suggested that perhaps the earth rotates on an axis every twenty-four hours, thereby explaining in a new way the rising and setting of the sun, moon, and stars. At a time when the motion of the heavenly bodies around the earth was the generally accepted theory, Heraclides' proposal became well-known but ill-received. In addition to his theory of the rotation of the earth, the claim that the motions of Mercury and Venus are centered on the sun has also been attributed to Heraclides.
Determination of ontological positions requires more information than the bare outlines of what an astronomer's theories were; to put Heraclides in either box requires knowing to what end he intended his theories. Speculation might lead to the conclusion that he was concerned with representing the actual nature of reality in his theories (in that he came up with a secondary theory for events which had already been explained another way), thereby making him a "realist." But ultimately, his 'whys' are not known today, and certain categorization of Heraclides in this regard is impossible.
A similar problem arises in attempting to evaluate another astronomer, Aristarchus of Samos (c. 310-230BC), who came a generation or two after Heraclides. Aristarchus proposed a heliocentric system, in which the sun is the fixed center of the cosmos, and the earth circles the sun as a planet. Like with Heraclides, it would be tempting to label Aristarchus a realist because he proposed a model that conforms to modern concepts of reality, but it is uncertain whether Aristarchus' model was the result of cosmological speculation, or whether it was proposed merely for its predictive benefits. At any rate, it was rejected on both grounds--realistically in that it violated ancient authority, common sense, religious belief and Aristotlelian physics (that is, contemporary sources of cosmological beliefs), and instrumentally in that it also predicted stellar parallax, which could not be observed.
These hypotheses were cited by Simplicius in a passage within his Commentary on Aristotle's Physics in which he delineated the boundaries of physical and mathematical astronomy. The astronomer, Simplicius said, often "invents by way of hypothesis, and states certain expedients by the assumption of which the phenomena will be saved." He thus viewed the heliocentric model, with a degree of incredulity, as an example of how far astronomers may go to find "different ways [by which] it is possible for these phenomena to be brought about". Such a strange viewpoint was possible because, according to Simplicius, "it is no part of the business of an astronomer to know what is by nature suited to a position of rest, and what sort of bodies are apt to move...[b]ut he must go to the physicist for his first principles". Thus Simplicius identified mathematical astronomy as the realm of generating and testing predictive hypotheses (to "save" phenomena), and physics as the realm of "consider[ing] the substance of the heaven and the stars".
Hipparchus is often called the "greatest astronomer in antiquity" (Neugebauer) but very little is known about him. The most comprehensive biographical knowledge is found in Ptolemy's Almagest, where he is named as Ptolemy's most influential predecessor. Hipparchus' foundation served as the growing point for Ptolemy's own better known astronomical models.
His astronomical models were both practical and theoretical, but his use of observations as methods for developing reliable prediction models implies his classification as an instrumentalist. His written works included criticism of previous astronomical works, works concerning optics, mathematics, geography, astrology, a star catalogue and an astronomical calendar. He is credited as having founded the field of Trigonometry, combining astronomical observations with mathematical interpretations of their respective models. Many of his mathematical advances show evidence of Babylonian, as well as Greek, influence. He noted the shift in the relative position of the solstices and equinoxes against a background of fixed stars. He also may have been the first to develop a reliable method of predicting solar eclipses. He also is credited in the Almagest as having invented the astrolabe, a device which allows a user on land to calculate his approximate latitude/longitude position by means of trigonometric evaluation of the celestial bodies
Few natural philosophers of the Hellenistic period were as influential in the field of astronomy as Ptolemy. As Ptolemy wrote over the course of time other scholars became obsolete and were therefore not transcribed as often; on the one hand, this was a tragedy for history as the world lost many of its articles evidencing early astronomical thought when astronomical thought of such caliber was still fledgling. However on the other, the world ultimately benefited from the natural philosophy of Ptolemy. His predictions stemmed from observations over a good portion of his lifetime, creating star and planet tables that were unparalleled in his time. Using these tools, Ptolemy made predictions to prove his hypotheses and possibly further refine his tables. He produced the Almagest, the premier text regarding astronomy in his time in not only Hellenistic Greece, but in the surrounding Latin territory.Its influence even reached the Islamic speaking natural philosophers of the time. His predictions, not his theories regarding why the heavens do what they do, earned him high regard. In that spirit, Ptolemy was an instrumentalistic natural philosopher.
In Ptolemy’s Tetrabiblos, the very first sentence advocates that understanding the movement of the planets is of greater importance than that of understanding why the planets move in that particular way. Ptolemy writes that “[o}f the means of prediction through astronomy, O Syrus, two are the most important and valid. One, which is first both in order and in effectiveness, is that whereby we apprehend the aspects of the movements of sun, moon, and stars in relation to each other and to the earth, as they occur from time to time; the second is that in which by means of the natural character of these aspects themselves we investigate the changes which they bring about in that which they surround” (Ptolemy, introduction, Book 1). He says that ways to apprehend the movements of the Sun, Moon, planets, and countless stars are greater in impact that those that simply theorize how those heavenly bodies accomplish that movement.
The website,http://people.scs.fsu.edu/~dduke/ptolemy.html ,conceptualizes concentric, nested circles used by Ptolemy to predict the stellar motions of the bodies within the realm of the stars. Ptolemy used and built on a pair of inventions of Apollonius, the eccentric and epicycle-deferent models of the universe, which he used to characterize the motions of the heavenly bodies. Ptolemy modified these to include a point called an equant, which was actually a point exactly opposite the observation point in reference to the center of orbit of the observable body. Using the equant as a factor in his mathematically (rather than observable reality) oriented models, Ptolemy predicted the movements of the other planets to a greater accuracy than those before him. These highly accurate models used mathematics to successfully predict the movement of the heavenly bodies rather than hypothesizing why their movements were as such. For these reasons, Ptolemy is incontrovertibly an instrumentalist.
The use of the eccentric model by Ptolemy, Apollonius and others illustrates instrumentalist philosophy well. The general consensus of ancient natural philosophers was that the earth was in the center of the universe; Aristotle and others posited reasons, from a realist perspective, for this to be the case. When mathematical astronomers adopted the eccentric model, they did not do so out of any disbelief in this position, but merely because, using the model, the math worked out. The eccentric and epicycle-deferent models allowed mathematical astronomers to retain uniform circular motion, which was easier to calculate (and, it should be noted, philosophically more desirable as well).
Plato and Aristotle help give the plain advantages to the realist point of view. Plato gave purpose back to life through realism when he created the Demiurge. Prior to Plato’s creation the philosophical world had begun to adopt an ontology that gave little to no purpose to people, Plato despised and feared this path of thought. Aristotle attributed to the realist advantage multiple reasons for the shape of the earth, the sphere. By his argument Aristotle gave the realist view multiple reasons to adopt the sphere as the shape of the earth. The realist point of view while it does not plan to predict it helps those who follow it to find understanding as to why the world works as it does.
However, while Plato and Aristotle give plain advantages to the realist point of view they also in doing so show the flaws with the view as well. Plato viewed the word as a projection of forms, which would then mean that you could never truly see reality. That does not pose very advantages when one wants to live in the real world. Plato also denied the thought of an earth without a cause. While this may seem nice it means that something must have a good reason or cause for, say, disease. This realist point of view then attributes things such as disease to a cause and not the possibility that they just happen. Aristotle, while a great thinker, did not have a way in which to prove his theories of change. He could reason as to why the four ideas of change must occur but he could never prove them because, like all realist the senses are not good enough to trust for true knowledge only reason can gain true knowledge. Possibly the greatest flaw in realism stems from its inability to predict what could happen. While reason may answer the question of “why” it never explains what will happen.
On one hand, the elements of predictive precision emphasized in an instrumentalist approach can be useful, regardless of a particular philosopher's cosmology. In the case of a realist like Aristotle, mathematical predictive ability in his theories of reality's nature demonstrates the accuracy of the theory in relation to the cosmos. Within Aristotle's system of thought, for example, syllogistic argument developed. Such an argument depended on systematic observation for the validity of its initial inductive claim, a means to knowledge that Aristotle advocated. Plato, perhaps, might have disagreed about the validity of sensory observation, but in any case, he admitted that the study of physics had its uses.
Neither is the instrumentalist constantly bogged down with details like theoretical representation of actual reality. When Ptolemy and others dismissed Aristarchus' heliocentric theory out of hand, they partially did so because it was unnecessary to their inquiries and calculations. Extraneous solutions created only so much fluff when they only needed one plausible solution to continue progressively with their work.
The obvious problem of this approach lies in that one annoying fact: the solar system is heliocentric; Aristarchus' model was correct in this respect. Though Ptolemy may have thought irrelevant, he took the time to refute the claim through argument using natural physics. He did it so soundly that everyone in the West took Aristarchus for a fool for centuries. One might argue that this hindered even the development of the mathematical side of astronomy, precisely because it was accepted as a true premise.
Curiosity creeps in fairly naturally, moreover, to hinder the pure instrumental thought. By age three, a person's constant refrain is "why;" small wonder that ephemerides and astrological prediction did not satisfy everyone or every time period. Realism has the added advantage of cosmological theory and quest. It is more natural in that it leans still more to the side of cause-seeking for natural events. Opposed to this approach, instrumental theory exists for the purposes of astrology and divination, following in the ancient Mesopotamian tradition. It seeks true knowledge from the stars themselves as revelation in which theories are used, if needed, to achieve clarity.
Ptolemy wrote early in the Almagest, “It is this love of contemplation of the eternal and unchanging which we constantly strive to increase, by studying those parts of these sciences which have already been mastered by those who approach them in a genuine spirit of inquiry, and by ourselves attempting to contribute as much advancement as has been made possible by the additional time between those people and ourselves” (Ptolemy, Almagest 37). Both Aristotle and Ptolemy, the prime examples of realism and instrumentalism respectively, exhibited “the love of contemplation of the eternal and unchanging” in their considerations of the celestial realm. While differing fundamentally in purpose and often approach, both systems of thought contain and contribute to a “genuine spirit of inquiry.”
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