Reading Questions: De Caelo I, 2-3


(Questions for reflection, which cannot necessarily be answered simply by reading the text but should be provoked by it, are marked with an asterisk.)


1. What, according to Aristotle, are the only simple motions? In what sense are they simple?


2. When an object is not a simple sort of substance but a compound, what determines the way that it will move?


3. If something is of such a nature as to move circularly, can it be made to move in any other fashion? If so how? If not why not?


4. What geometric shape, according to Aristotle, is "perfect"? Why is such motion "prior" to linear motion?


*5. What is the point of having a notion of "natural" motion -- what role does it play? In contemporary science, do we still have the idea of "natural" motion or have we got rid of it?


6. What is Aristotle's argument against the possibility that the circular motion of rotating bodies about the center is unnatural?


7. What is Aristotle's definition of "light" and "heavy"? What is distinctively Aristotelian about the way that these terms are defined?


8. What does Aristotle mean when he says that everything that moves up or down possesses lightness or heaviness, "but not both [i.e., not both qualities] relatively to the same thing"?


9. Aristotle argues that things that move with a circular motion [i.e. the sun, moon, stars and planets] cannot be either naturally or unnaturally moved toward or away from the center of all things. What is his argument? How does "unnatural" get used here?


10. For what sort of motion, according to Aristotle, is there no contrary? Try to work out what he means here.


11. How does circular motion get linked to indestructibility? Try to express this as an argument, using the clues in the text.


12. Aristotle gives an argument from the observation of natural bodies in two paragraphs near the end of chapter 3. What is the conclusion of this argument? What is its structure? How strong does he seem to think it is?