INTRODUCTION
Arisstotle account of physics is very sophisticated and dynamic. However Aristotle’s account of motion can be found in the Physics. By motion, Aristotle understands any kind of change. He defines motion as the actuality of a potentiality. Initially, Aristotle's definition seems to involve a contradiction. However, commentators on the works of Aristotle, such as St. Thomas Aquinas, maintain that this is the only way to define motion.
The definition is a conjunction of two terms which normally contradict each other, along with, in Greek, a qualifying clause which seems to make the contradiction inescapable. Yet St. Thomas Aquinas called it the only possible way to define motion by what is prior to and better known than motion. At the opposite extreme is the young Descartes, who in the first book he wrote announced that while everyone knows what motion is, no one understands Aristotle's definition of it. According to Descartes, "motion . . . is nothing more than the action by which any body passes from one place to another"
From the Middle Ages to modern times, commentators disagreed on the interpretation of Aristotle’s account of motion. An accurate rendering of Aristotle's definition must include apparently inconsistent propositions: that motion is rest, and that a potentiality, which must be, if anything, a privation of actuality, is at the same time that actuality of which it is the lack. St. Thomas Aquinas was prepared to take these propositions seriously. St. Thomas observes that to say that something is in motion is just to say that it is both what it is already and something else that it is not yet. Accordingly, motion is the mode in which the future belongs to the present, it is the present absence of just those particular absent things which are about to be. St. Thomas thus resolves the apparent contradiction between potentiality and actuality in Aristotle's definition of motion by arguing that in every motion actuality and potentiality are mixed or blended. For the purpose of this work however it will be fitting to dazzle into the concept of Aristotle motion using the following thematic outline:
The nature of Aristotle's Motion
The concept of actuality and potentiality
Thomas' Account of Aristotle's View of Motion
Unmoved mover
Evaluation
Conclusion
The nature of Aristotle's motion
Aristotle discusses motion in his Physics quite differently from modern science. Aristotle's definition of motion is closely connected to his actuality-potentiality distinction. Taken literally, Aristotle defines motion as the actuality of a "potentiality as such" What Aristotle meant however is the subject of several different interpretations. A major difficulty comes from the fact that the terms actuality and potentiality, linked in this definition, are normally understood within Aristotle as opposed to each other.
On the other hand the "as such" is important and is explained at length by Aristotle, giving examples of "potentiality as such". For example the motion of building is the actuality of the potentiality of the building materials as building materials as opposed to anything else they might become, and this potential in the unbuilt materials is referred to by Aristotle as "the buildable". So the motion of building is the actualization of "the buildable" and not the actualization of a house as such, nor the actualization of any other possibility which the building materials might have had.
Motion is a continuum: a mere series of positions between A and B is not a motion from A to B. If X is to move from A to B, however, it must pass through any intermediate point between A and B. But passing through a point is not the same as being located at that point. Aristotle argues that whatever is in motion has already been in motion. If X, traveling from A to B, passes through the intermediate point K, it must have already passed through an earlier point J, intermediate between A and K. But however short the distance between A and J, that too is divisible, and so on ad infinitum. At any point at which X is moving, therefore, there will be an earlier point at which it was already moving. It follows that there is no such thing as a first instant of motion.
The concept of actuality and potentiality
In philosophy, potentiality and actuality are principles of a dichotomy which Aristotle used to analyze motion, causality, and principles in his Physics, The concept of potentiality, in this context, generally refers to any "possibility" that a thing can be said to have. Aristotle did not consider all possibilities the same, and emphasized the importance of those that become real of their own accord when conditions are right and nothing stops them. Actuality, in contrast to potentiality, is the motion, change or activity that represents an exercise or fulfillment of a possibility, when a possibility becomes real in the fullest sense.
Actuality comes from Latin actualitas and is a traditional translation, but its normal meaning in Latin is "anything which is currently happening". The two words energeia and entelecheia were coined by Aristotle, and he stated that their meanings were intended to converge. In practice, most commentators and translators consider the two words to be interchangeable. They both refer to something being in its own type of action or at work, as all things are when they are real in the fullest sense, and not just potentially real. For example, "to be a rock is to strain to be at the center of the universe, and thus to be in motion unless constrained otherwise"
Thomas' Account of Aristotle's View of Motion
St. Thomas Aquinas, in his interpretation of Aristotle's definition of motion, that Aristotle meant what he wrote, and that what Aristotle wrote is worth the effort of understanding. Thomas explains clearly and simply a sense in which Aristotle's definition is both free of contradiction and genuinely a definition of motion. One must simply see that the growing puppy is a dog, that the half formed lump of bronze on which the sculptor is working is a statue of Hermes, that the tepid water on the fire is hot; what it means to say that the puppy is growing, the bronze is being worked, or the water is being heated, is that each is not just the complex of characteristics it possesses right now; in each case, something that the thing is not yet, already belongs to it as that toward which it is, right now, ordered. To say that something is in motion is just to say that it is both what it is already and something else that it isn't yet. What else do we mean by saying that the puppy is growing, rather than remaining what it is, that the bronze under the sculptor's hand is in a different condition from the identically shaped lump of bronze he has discarded, or that the water is not just tepid but being heated? Motion is the mode in which the future belongs to the present, is the present absence of just those particular absent things which are about to be.
Thomas discusses in detail the example of the water being heated. Assume it to have started cold, and to have been heated so far to room temperature. The heat it now has, which has replaced the potentiality it previously had to be just that hot, belongs to it in actuality. The capacity it has to be still hotter belongs to it in potentiality. To the extent that it is actually hot it has been moved; to the extent that it is not yet as hot as it is going to be, it is not yet moved. The motion is just the joint presence of potentiality and actuality with respect to same thing, in this case heat.
In Thomas' version of Aristotle's definition one can see the alternative to Descartes' approach to physics. Since Descartes regards motion as ultimate and given, his physics will give no account of motion itself, but describe the transient static configurations through which the moving things pass. By Thomas' account, motion is not ultimate but is a consequence of the way in which present states of things are ordered toward other actualities which do not belong to them. One could build on such an account a physics of forces, that is, of those directed potentialities which cause a thing to move, to pass over from the actuality it possesses to another which it lacks but to which it is ordered. Motion will thus not have to be understood as the mysterious departure of things from rest, which alone can be described, but as the outcome of the action upon one another of divergent and conflicting innate tendencies of things.
The unmoved mover
Since the motion it causes is everlasting, this X must itself be an eternal substance. It must lack matter, for it cannot come into existence or go out of existence by turning into anything else. It must also lack potentiality, for the mere power to cause motion would not ensure the sempiternity of motion. It must, therefore, be pure actuality. Although the revolving heavens, for Aristotle, lack the possibility of substantial change, they possess potentiality, because each heavenly body has the power to move elsewhere in its diurnal round. Since these bodies are in motion, they need a mover, and this is a motionless mover. Such a mover could not act as an efficient cause, because that would involve a change in itself, but it can act as a final cause—an object of love—because being loved does not involve any change in the beloved. The stars and planets seek to imitate the perfection of the unmoved mover by moving about the Earth in a circle, the most perfect of shapes. For this to be the case, of course, the heavenly bodies must have souls capable of feeling love for the unmoved mover. “On such a principle,” Aristotle says, “depend the heavens and the world of nature.”
Aristotle is prepared to call the unmoved mover “God.” The life of God, he says, must be like the very best of human lives. The delight that a human being takes in the sublimest moments of philosophical contemplation is in God a perpetual state. What, Aristotle asks, does God think of? He must think of something—otherwise, he is no better than a sleeping human—and whatever he is thinking of, he must think of eternally. Either he thinks about himself, or he thinks about something else. But the value of a thought depends on the value of what it is a thought of, so, if God were thinking of anything other than himself, he would be somehow degraded. So he must be thinking of himself, the supreme being, and his life is a thinking of thinking.
This conclusion has been much debated. Some have regarded it as a sublime truth; others have thought it a piece of exquisite nonsense. Among those who have taken the latter view, some have considered it the supreme absurdity of Aristotle’s system, and others have held that Aristotle himself intended it as a reductio ad absurdum. Whatever the truth about the object of thought of the unmoved mover, it seems clear that it does not include the contingent affairs of individual human beings. Thus, at the supreme point of Aristotle’s causal hierarchy stand the heavenly movers, moved and unmoved, which are the final cause of all generation and corruption.
Evaluative Conclusion
Consider the application of Aristotle's account of motion this paradox famous in antiquity. Zeno argued in various ways that there is no motion. According to one of his arguments, the arrow in flight is always in some one place, therefore always at rest, and therefore never in motion. We can deduce from Aristotle's definition that Zeno has made the same error, technically called the fallacy of composition, as one who would argue that no animal is alive since its head, when cut off, is not alive, its blood, when drawn out, is not alive, its bones, when removed are not alive, and so on with each part in turn
Aristotle theory of motion cannot be overemphasized in a nutshell. Infact this theory cuts across almostall this physics. Despiteof all the critiques he theory still gold much fact in philosophocal entreprise.
Bilblography
See Aristotle motion in "www.iep.utm.edu/aris-mot/" retrieved 02/06/2015
http://www.britannica.com/EBchecked/topic/34560/Aristotle/254718/The-unmoved-mover
Aristotle, Du ciel, (De Caelo = On the Heavens), Greek text and French translation by Paul Moraux, Paris: Les Belles lettres (Collection Budé), 1965.
Aristotle, Physics, Books I-II, translated with introduction and notes by William Charlton, Oxford: Clarendon Press (Clarendon Aristotle Series), 1970 (2nd. ed. 1992)
Aristotle's Natural Philosophy: Movers and Unmoved Mover
Sachs, Joe. "Aristotle: Metaphysics" . Internet Encyclopedia of Philosophy.
Kosman, L. A. "Aristotle's Definition of Motion," Phronesis, 1969.
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