Here are the examples we practiced on in class on Wednesday, March 22. I’ll do the first example to give you an idea of what I’m looking for.
Gupp E. looks at a fish tank and says, “That ten-gallon aquarium contains forty fish. If that ten-gallon aquarium contains forty fish, then that aquarium is too crowded. Therefore, that aquarium is too
crowded.”
First identify logical connectives (if, then, and therefore). Here the logical connectives are in red.
Gupp E. looks at a fish tank and says, “That ten-gallon aquarium contains forty fish. If that ten-gallon aquarium contains forty fish, then that aquarium is too crowded. Therefore, that aquarium is too crowded.”
Then try to extract the logical form of the argument. We will use P and Q, but you may use different letters. The segment we will identify as P is in blue and the segment we will identify as Q is in yellow.
Gupp E. looks at a fish tank and says, “That ten-gallon aquarium contains forty fish. If that ten-gallon aquarium contains forty fish, then that aquarium is too crowded. Therefore, that aquarium is too crowded.”
Notice that now we have the following argument form (remember I can’t represent symbols on the web page):
P implies Q
P
----------
Q
This is an example of Modus Ponens. The argument is valid.
A fetus is either a person with rights or a mere bundle of cells. If it is a mere bundle of cells, it is morally similar to a wart or a mole. But nobody thinks a fetus is like a wart or a mole.
To display true altruism, a person must behave in a way that is harmful to herself and beneficial to others. Evolutionary theory tells us that people, since they are the product of evolution, always act in ways to maximize their chances for survival. So they always act selfishly. Thus, people never display true altruism.
If the debt continues to grow at the alarming pace
of last few years, real interest rates will have to rise in order to make
bonds, treasury bills and the like more attractive. If real interest rates
rise, then more Americans, who now have extremely high rates of personal debt,
will declare personal bankruptcy. Therefore, if the debt continues to grow,
more Americans will declare personal bankruptcy.
“Either it is an accident that I choose to act as I
do or it is not. If it is an accident,
then it is merely a matter of chance that I did not choose otherwise; and if it
is merely a matter of chance that I did not choose otherwise, it is surely
irrational to hold me morally responsible for choosing as I did. But if it is
not an accident that I choose to do one thing rather than another, then
presumably there is some causal explanation of may choice: and if that case we
are led back to determinism [which would mean that we aren’t morally
responsible for what we do].”--A.J. Ayer: Freedom
and Necessity
If oil prices go up, then there will be a recession. If there is another war then oil prices will go up. If there is a recession, then the president will not be reelected. The president wants to be reelected. If the president wants to be reelected, then he will try to prevent a war. Therefore, the president will try to prevent a war.