## Create a counterexample or model to show that the following deductive arguments are invalid.

Practice 1F I in your book, do numbers 3, 7, 8, 16, 18, 19, and 20.

Example :

1. Create a counterexample or model to show that the following deductive arguments are invalid.
2. All towers less than 200 years old are skyscrapers. All buildings made of steel are skyscrapers. Therefore, all buildings made of steel are towers less than 200 years old.

Answer: If we let T = towers less than 200 years old, S = skyscrapers, and B = buildings made of steel, then the argument form is the following: All T are S. All B are S. All B are T.

1. All Phi Beta Kappa members are seniors in college. All Phi Beta Kappa mem-bers are liberal arts majors. Therefore, all liberal arts majors are seniors in college.
2. All skateboards are items made of wood. All items made of wood are flammable objects. Therefore, all flammable objects are skateboards.
3. No skateboards are items made of wood. No items made of wood are flammable objects. Therefore, no flammable objects are skateboards.
4. All psychiatrists are people with medical degrees. All people who can prescribe drugs are people with medical degrees. Therefore, all psychiatrists are people who can prescribe drugs.
5. All members of the U.S. Congress are citizens of the United States. All people under 21 years of age are citizens of the United States. Therefore, no people under 21 years of age are members of the U.S. Congress.
6. All humans are things that contain carbon. All inanimate objects are things that contain carbon. Therefore, all humans are inanimate objects.
7. No coal mines are dangerous areas to work. All dangerous areas to work are places inspected by federal agencies. Therefore, no coal mines are places inspected by federal agencies.