Aristotle the GreatAristotle the Great

Logic rules over experimental Logic rules over experimental proof!!!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 AristotleCosmology de Aristotle

Heavenly bodies have natural circular Heavenly bodies have natural circular motion because they are perfect and motion because they are perfect and unchangingunchanging

Requires Ptolemaic Machine to rectify Requires Ptolemaic Machine to rectify observations against this proclamationobservations against this proclamation

With this machine, planetary predictions With this machine, planetary predictions could be made with good accuracycould be made with good accuracy

This gives the model real powerThis gives the model real power No observation strongly rules out modelNo observation strongly rules out model

Analyze ThisAnalyze This "Now since changes are of four kinds-"Now since changes are of four kinds-

either in respect of the 'what' or of the either in respect of the 'what' or of the quality or of the quantity or of the quality or of the quantity or of the place, and change in respect of place, and change in respect of 'thisness' is simple generation and 'thisness' is simple generation and destruction, and change in quantity is destruction, and change in quantity is increase and diminution, and change increase and diminution, and change in respect of an affection is alteration, in respect of an affection is alteration, and change of place is motion, and change of place is motion, changes will be from given states into changes will be from given states into those contrary to them in these those contrary to them in these several respects."several respects."

Aristotle’s Laws of MotionAristotle’s Laws of Motion

There is no motion without a forceThere is no motion without a force Speed is proportional to force and Speed is proportional to force and

inversely proportional to resistanceinversely proportional to resistance Qualitatively this implies that a body will Qualitatively this implies that a body will

traverse a thinner medium in a shorter traverse a thinner medium in a shorter time than a thicker medium (of the same time than a thicker medium (of the same length): things will go faster through air length): things will go faster through air than through waterthan through water..

Test this ideaTest this idea

Testing and QuestionsTesting and Questions

Class Discussion Question: What is the Class Discussion Question: What is the logical consequence of motion in a logical consequence of motion in a vacuum, under this hypothesisvacuum, under this hypothesis??

For falling bodies, the force is the For falling bodies, the force is the weight pulling down a body and the weight pulling down a body and the resistance is that of the medium (air, resistance is that of the medium (air, water, etc.). Aristotle noted that a water, etc.). Aristotle noted that a falling object gains speed, which he falling object gains speed, which he then attributed to a gain in weightthen attributed to a gain in weight..

Falling ObjectsFalling Objects

If initial weight determines the speed If initial weight determines the speed of fall, then when two different of fall, then when two different weights are dropped from a high weights are dropped from a high place the heavier will fall faster and place the heavier will fall faster and the lighter slower, in proportion to the lighter slower, in proportion to the two weights. A 10 lb weight the two weights. A 10 lb weight would reach Earth by the time a 1 lb would reach Earth by the time a 1 lb weight had fallen one-tenth as farweight had fallen one-tenth as far

Oh yeah, sucker, prove it ….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:

Aristotle’s CannonAristotle’s Cannon

Experiments ShowExperiments Show

Aristotle’s logical thinking of motion and Aristotle’s logical thinking of motion and falling bodies fails all experimental tests falling bodies fails all experimental tests universally.universally.

Indeed, Archimedes (~250 BC) realized Indeed, Archimedes (~250 BC) realized projectile motion was parabolic and devised projectile motion was parabolic and devised effective catapults to lob quarter ton stones effective catapults to lob quarter ton stones and those damn Romansand those damn Romans