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Aristotle the Great. Logic rules over experimental proof!!!. Aristotle the Vague.
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Aristotle the Great Logic rules over experimental proof!!!
Aristotle the Vague • That a final cause may exist among unchangeable entities is shown by the distinction of its meanings. For the final cause is (a) some being for whose good an action is done, and (b) something at which the action aims; and of these the latter exists among unchangeable entities though the former does not. The final cause, then, produces motion as being loved, but all other things move by being moved. Now if something is moved it is capable of being otherwise than as it is. Therefore if its actuality is the primary form of spatial motion, then in so far as it is subject to change, in this respect it is capable of being otherwise,--in place, even if not in substance. But since there is something which moves while itself unmoved, existing actually, this can in no way be otherwise than as it is. For motion in space is the first of the kinds of change, and motion in a circle the first kind of spatial motion; and this the first mover produces. The first mover, then, exists of necessity; and in so far as it exists by necessity, its mode of being is good, and it is in this sense a first principle. For the necessary has all these senses--that which is necessary perforce because it is contrary to the natural impulse, that without which the good is impossible, and that which cannot be otherwise but can exist only in a single way. (Metaphysics, Book XII, Chapter 7, 1072)
Prime Mover • There is a privileged being: The Prime Mover. He is the first agent, responsible for moving objects, which, in turn, move other objects. • The Prime Mover, he argued, must be at Absolute Rest. By "absolute" rest , we mean that all observers will universally agree on that state of rest
Cosmology de Aristotle • Heavenly bodies have natural circular motion because they are perfect and unchanging • Requires Ptolemaic Machine to rectify observations against this proclamation • With this machine, planetary predictions could be made with good accuracy • This gives the model real power • No observation strongly rules out model
Analyze This • "Now since changes are of four kinds-either in respect of the 'what' or of the quality or of the quantity or of the place, and change in respect of 'thisness' is simple generation and destruction, and change in quantity is increase and diminution, and change in respect of an affection is alteration, and change of place is motion, changes will be from given states into those contrary to them in these several respects."
Aristotle’s Laws of Motion • There is no motion without a force • Speed is proportional to force and inversely proportional to resistance • Qualitatively this implies that a body will traverse a thinner medium in a shorter time than a thicker medium (of the same length): things will go faster through air than through water. • Test this idea
Testing and Questions • Class Discussion Question: What is the logical consequence of motion in a vacuum, under this hypothesis? • For falling bodies, the force is the weight pulling down a body and the resistance is that of the medium (air, water, etc.). Aristotle noted that a falling object gains speed, which he then attributed to a gain in weight.
Falling Objects • If initial weight determines the speed of fall, then when two different weights are dropped from a high place the heavier will fall faster and the lighter slower, in proportion to the two weights. A 10 lb weight would reach Earth by the time a 1 lb weight had fallen one-tenth as far • Oh yeah, sucker, prove it ….
Projectile Motion • In Aristotle's view, objects moved parallel to the Earth's surface until it was time (i.e. it was their destiny) to fall back to the earth • When a stone is thrown, an impetus is given to it to disturb it from its natural condition. Gradually the stone “forgets” this impetus and falls back to its natural place:
Experiments Show • Aristotle’s logical thinking of motion and falling bodies fails all experimental tests universally. • Indeed, Archimedes (~250 BC) realized projectile motion was parabolic and devised effective catapults to lob quarter ton stones and those damn Romans
