Argument Validity

Exercise 7-9
Given the premises, discuss whether the conclusion of each argument that
Follows is (a) true beyond a reasonable doubt, (b) probably true, or (c) possibly
True or possibly false. You should expect disagreement on these items, but the
closer your answers are to your instructor’s, the better.

2. The annual rainfall in California’s north valley averages twenty-three
inches. So the rainfall next year will be twenty-three inches.
The premise that something that happened in the past will happen in the future is fallacious.   Although there is an average amount of rainfall in California, the average does not represent an actual yearly amount of rainfall.   Therefore the prediction for 23 inches of rain is not strong, and can be considered possibly false or possibly true.
3. You expect to get forty miles to the gallon in that? Why, that old wreck
has a monster V8; besides, it’s fifty years old and needs an overhaul.
The premises are that the vehicle requires an overhaul, it has a monster V8, and it is old.   These conditions would make it seem as though this vehicle wouldn’t be able to achieve 40 mpg.   However, we are not informed about the rest of the vehicle.   This particular model may be very fuel efficient or has been modified to get better miles per gallon.   As a result the conclusion is probably true, but not absolutely true.
4. In three of the last four presidential races, the winner of the Iowa Republican
primary has not captured the Republican nomination. Therefore,
the winner of the next Iowa Republican primary will not capture the
Republican nomination.
The premise that the past predicts future results is fallacious.   Wining the Iowa Republican primary would not preclude a candidate from winning the party’s nomination.   The conclusion was based on the last three out of four years.   That does not guarantee that history will be repeated.   However, it is common that things happen that influences outcomes, and that there is...