Thursday, July 13 2000
Quiz 3
Name: _______________________________
An argument is sound, if it is valid and
its premises are true. (Handout #5).
An argument is formal if the validity of the argument does not
depend on the meaning of the symbols employed. (Handout #5).
From the assumption A and the derivation of a contradiction you
infer `not A'. (Lecture 7/12/00)
A
:
:
Contradiction
---------
not A
Assume: God does not exist.
Then, there is something more perfect
than God, by assumption (b).
In other words, God is not the most perfect being.
This contradicts the assumption (a).
Therefore, by reductio ad absurdum, God does exist. (This argument is
attributed to Descartes.)
The argument is not valid. Because it is
possible for the premises to be true, but the conclusion to be
false, for example, if my income rises because of a raise and
not because of the lowering of my taxes. (Lecture 7/11/00)